I was reading another thread about someone asking if they could maintain a concentration spell and cast another concentration spell that does instant damage, which I already knew they couldn’t, and the thread confirmed this. That thread got me thinking about the paladin I play, I have just turned level 4, but due to the small amount of spell slots available to me, I have been reluctant to use them just in case I need them for a later fight. I have over the last couple of sessions started using my smites due to the enemies getting stronger and am wondering if I am understanding the concentration correct.

I spend the slot to cast a smite as a bonus action then attack with my action. I miss, so I must maintain concentration on the spell to allow my next turn to have the possibility of the smite damage/effect.

Am I correct with this?

I spend the slot to cast a smite as a bonus action then attack with my action. I hit, then the following happens.

Searing smite: 1d6 fire damage on the hit & maintain concentration so they continue to take (the same? Or the 1d6 rolled every turn?) fire damage due to being on fire

Thunderous smite: 2d6 thunder damage on the hit and they are thrown back and fall prone, then spell ends, no concentration needed.

Wrathful smite: 1d6 psychic damage on the hit & maintain concentration to maintain the frightened status

Am I correct with this?

I know the damage happens but the effects wont happen if the enemy makes their save, so the examples assume they don’t.

You're correct on all your statements. For searing smite, it's a d6 rolled each turn. (Not the same initial roll taken over and over.)

Thanks for the answer. i am new to d&d, only DMed one session and played some sessions as a PC. I have watched critical role and some of dimension 20, and think i understand the rules but keep second guessing myself when i read these forums.

Overall, you are better off "burning" your spell slots for Divine Smite than casting the Smite spells.  No concentration, the trigger is to hit a creature, so it is 100% guaranteed increase in damage.  No saves, just pure extra damage.

True for most situations, but the effects of the smite spells can come in pretty handy situationally. 9 times out of 10, dropping a divine smite on a critical hit is what most people save them for. But getting a branding smite on a creature that likes to use invisibility (for example) is the better choice vs using that slot for a divine smite. Again, very situational though. 

yeah the wrathful smite worked in one of the sessions quite well. we are playing through "lost mines of phandalin (sp?)" and were in cragmaw castle and i caused the king to become frightened and run away on either the first or second round, and he hid in another room with me standing at the door so he couldn't escape.

Every smite has their purpose: I used to think Searing smite was worthless, but it's actually one of the few smites that can scale with spell slot level. If you're ever a  2 Pala/ 18 Sorc who needs to imbue their sword with a 9th level searing smite, you can do that *chuckle*

But yea I don't know how searing smite's concentration works either. It's unclear, but I wouldn't think you need to continue the concentration to maintain it's effect.

This is a confusing part on concentration on smite spells.
You 100% need to concentrate on the spell before you hit.

What isn't that clear is if you still need to concentrate afterward to maintain effects after hit.

When you think about it, concentration requirement in itself means you will need to drop bless or shield of faith that you could cast before hand. At the same time, effects of these spells aren't that good to warrant concentration. They allow continues saving throws, they are single target... If you compare them to other spells that require concentration as balancing factor, i don't think these warrant that. Add limited spell slots of Paladin and I come to the conclusion that you shouldn't need to concentrate after you hit your target.

Was it clarified anywhere?

Thought?

If we look at Branding Smite as an example, it says about the ongoing effect (emphasis is mine):

...and the target sheds dim light in a 5-foot radius and can’t become invisible until the spell ends.

So if you drop concentration after making the hit, the spell ends, and the ongoing effect will no longer trigger.  The other smite spells use similar wording to indicate that you must keep concentrating on them to get the lingering effects.

You need to concentrate before the hit lands, which ends concentration on other spells even if the smite has no ongoing effect.  You need to maintain concentration after the hit lands if the smite has any ongoing effects.

Most smite spells are, most of the time, worse than divine smite.  Divine smite does more damage, usually of a better damage type, without burning a bonus action or concentration, without allowing any saving throw, and is used after you already know you hit.

That said, some of the secondary effects of some of the smite spells are, situationally, useful enough to justify them.  Wrathful Smite in particular can be useful when going up against big brutes with bad wisdom saves (think ogres or hill giants), and Thunderous Smite is worth preparing if one or more of your party members likes to cast spells with ongoing area effects like Web, Wall of Fire, or Black Tentacles.

But "situational" really is the best word to use, and several of the smite spells don't even clear that low bar.