I think that marijuana smoking is not really a good idea for poker player. it makes you less alert, often causes attention failures, makes you much more susceptible to errors in judgement or simly errors due to attention insufficiency. This would be in my opinion general case of marijuana "enhanced" poker session. But also there can be exceptional cases like e.g. whensomebody is a real pot addict, he smokes it regularly and in high dosages (I mean dosages only administered by addicts who already built a strong tolerance for THC consumption which in result has chronic effects on such smokers which are different from general effects induced when smoking occasionaly (without habit,constant overdosing and addiction).
For such individuals smoking might have different influence on poker performance when playing, or, maybe more likely, they would be affected negatively by non-smoking which would induce withdrawal-like symptoms on them