Six male and four female healthy volunteers were given oral placebo (glucose capsule and orange juice), cannabidiol (CBD 200 mg capsule and orange juice), alcohol (1 g/kg in orange juice and glucose capsule), and CBD (200 mg capsule) plus alcohol (1 g/kg in orange juice) in a double-blind, crossover, randomized design. Treatments were spaced one week apart. Parameters measured were a finger tap test (motor performance), cancellation and differential aptitude tests (psychomotor performance), a 1-min time production task, subjective effects (66 item adjective-pair semantic differential), and breathalyzer estimations of blood alcohol levels. Compared to placebo, alcohol and alcohol plus CBD, but not CBD alone, produced significant impairments of motor and psychomotor performances, overestimations of time production and subjective responses indicating an accurate self-perception of their intoxication and deficits. The combination of alcohol plus CBD resulted in significantly lower blood alcohol levels compared to alcohol given alone, however, there were few differences observed between the pharmacological effects of the two alcohol conditions. Thus, the inactivity of CBD, a major marijuana constituent, on motor and mental performance and effects also extends to its interaction with alcohol.