Systematic screening of problematic cannabis use does not include the motivations that lead to consumption, although from a person-centered perspective this is fundamental. The present study explores the motivations for cannabis use in adults and its relationship with cannabis use patterns and problematic use. Adult cannabis users (previous 60 days) were recruited in the province of Barcelona (n = 468). Information on their sociodemographic data, cannabis use pattern, Cannabis Abuse Screening Test (CAST) and the main motivation for use were collected. Motivations were categorized a posteriori according to the Marijuana Motives Measures (MMM). A descriptive and inferential analysis was carried out to link the motivations to sociodemographic variables, consumption pattern and probability of suffering problematic cannabis use (CAST). Using cannabis to heighten positive feelings (35%), out of habit (29%) and to cope with negative feelings (25%) were the most frequent motivations. In comparison to other motivations, coping is related to a greater quantity of cannabis used (4 vs 3 joints per day, p = 0.005), higher probability of problematic cannabis use (77% vs 64%, p = 0.05), and greater social vulnerability (unemployment 56% vs 37%, p = 0.001; and low educational level 14% vs 8%, p = 0.042). Coping as a motivation for cannabis use is present in one out of four users and is a marker of social vulnerability, greater quantity of cannabis used and higher risk of problematic use. Patient-centered care together with preventive (emotional and social education) and clinical strategies (psychotherapy) can be useful for this population at higher risk.