This paper analyses the influence of and possible interaction between chronotype (Morning-types, Neither-types and Evening-types} and personality dimensions (neuroticism, extroversion and psychoticism) in the daily consumption of alcohol and psychostimulants (nicotine and caffeine). In a sample of 537 subjects (257 men and 280 women), who were students and professionals with different but fixed work schedules, there were significant differences among the chronotypes regarding the consumption of all the above. Evening-types consumed more alcohol, nicotine and caffeine (coffee and cola), while Morning-types consumed more caffeine from tea. Personality was only related to the consumption of cola: the greater the neuroticism the higher the consumption of this beverage. Stimulant drinks showed various types of interaction with personality types, which revealed a complex pattern of group action. The results stress the need to consider chronotype as a contributory psychological factor in a multi-causal model of consumption of psychoactive substances.