Cheating refers to any manner of play which violates the rules of the game and gives a player an unfair advantage. In poker the two most common forms involve manipulation of the deck or collusion.

Deck manipulation may involve card marking or trick dealing. With card marking a player will know the cards to be dealt and those of his opponents. With trick dealing that player, when it is his/her turn to deal, will shuffle and deal cards in a non-random fashion. Such cheating is generally not possible with dedicated dealers and in online poker rooms.

Collusion is likely the more insidious form of cheating. This is when two, or more, players are secretly acting as a team at the table. They exchange knowledge of their cards and engage in several tactics to manipulate pot size to their advantage. Collusion is harder for a typical player to spot online than in a real casino.