To identify the differences in the ASI-6 scores according to main substance of consumption among patients with drug use disorder who were included at the study of adaptation-validation of the Addiction Severity Index 6^th version (ASI-6) into Spanish.

Multicentre, observational, longitudinal, prospective study. 186 substance dependent/abuser individuals were included. Assessments were made with the Spanish ASI-6.

Main substance of consumption: 57% alcohol, 19.9% cocaine and 19.4% opiates. Men were 77.4% vs. 81.1% vs. 83.3% (p n.s.), mean ages were 47.12 (SD 10.18) vs. 32.62 (SD 8.20) vs. 36.47 (SD 8.04) years (p< 0.001), and 25.5% vs. 64.9% vs. 55.6% were single (p< 0.001). The greatest severity was found in the Alcohol area in the case of alcohol users (56.86) and in the Family/Social Partner Problems area in the case of cocaine and the opiate users (50.43 and 51.22). Alcohol users had statistically significant greater severity than the other two groups in the Alcohol area (56.86 vs. 49.38 vs. 45.17, p< 0.001) and tended to have lower severity in the Legal area than cocaine users (46.78 vs. 48.43, p 0.079).

Cocaine users were the youngest and used to be single. The ASI-6 only differentiated in the severity of the Alcohol area. Further studies including a higher proportion of cocaine and opiate users are needed.