This study identify mental disorders, the levels of impulsivity and aggressiveness of users of psychoactive substances in the homeless population. This is a descriptive, observational and cross-sectional study. The data were collected in welcoming communities and the Specialized Center for the Homeless Population. 52 subjects were studied, most of whom were male, single and with a low educational level. The most prevalent mental disorders found were the current major depressive episode, suicide risk, alcohol dependence / abuse. The mean total impulsivity score was 71.6 (SD ± 10.7) and as for the subcategory with the highest score, impulsiveness due to non-planning stood out (mean: 26.2; SD ± 5.2). As for the levels of aggressiveness, a total score was obtained (mean: 84.7; SD ± 21.9) with a higher score for aggressiveness (mean: 19; SD ± 21.9). Drug use showed a high frequency of mental disorders and high levels of impulsivity and aggression.