The aim of the present study was to analyze how the relationship that adolescents keep with their peer group (e.g., kind of activities performed in group, drug use by friends, and nature of their relationship) influence drug use. A sample of 1570 adolescents of both sexes (54.4% men and 45.6% women) belonging to the Autonomous Community of Madrid was used. The results showed that several substances studied were empirically grouped into three factors called «legal drugs», «medical drugs» and «illegal drugs». At the same time several stepwise regression analyses were conducted, considering the three factors as dependent variables, and
once more it was confirmed that the best predictor to explain the consumption of the different drugs was the fact of having friends that consumed tobacco, alcohol and marijuana.