[pocket3s]

I say check here because we need more info . What we know is this He thinks big pairs are just as valuable as they are in holdem and will prob call you with one which makes him a 66% fave here, He DOES NOT have a set because he didn't raise you after the flop(he prob has an overpair), His options are check behind you which gives you a free chance to try to catch one of your 18 cards on the river or he could bet which at most could be the pot, if he does that you have 2 to 1 on your money which is what you need to justify a call here. I check/call which I know seems kind of passive here, but you have Q high here and a guy too stupid to fold.