Cannabis is known to have effects on cognition in the hours after use (acute effects) and effects that are apparent even after the intoxication dissipates (chronic effects). The acute effects of cannabis are most notable on the cognitive domains of learning and memory, attention, and executive function. Cannabis contains numerous compounds (cannabinoids), and the two most frequently studied are delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD). Cannabis is known to have its impairing and intoxicating effects through THC, and there is some evidence that the nonpsychoactive CBD may affect cognitive function. The purpose of the present review is to compile the evidence for acute effects of cannabis on cognition, examined for each of THC and CBD. The cognitive domains of learning and memory, attention, and executive function are explored separately. The sections on the effects of THC or CBD on cognition end with a proposed mechanism of action. This review ends by exploring some avenues for future research, including understanding the chronic effects of cannabis on cognition, studying different routes of administration, and examining tolerance to cannabis.