<i>Aims:</i> Our aim was to further assess the Severity of Dependence Scale (SDS) validity and to identify the cut-off score for a DSM-IV diagnosis of heroin and cocaine dependence through a cross-sectional survey in Barcelona, Spain. <i>Methods:</i> The Psychiatric Research Interview for Substance and Mental Disorders (PRISM) was used as the gold standard. 146 young (18–30 years old) heroin users were recruited from outside the healthcare context, 135 of whom were also current cocaine users. SDS scores were correlated to quantity, frequency and length of drug use. <i>Results:</i> The SDS cut-off point at which there was optimal discrimination of a DSM-IV diagnosis presence was found to be 3 (i.e., a score of 3 or more) for heroin dependence and 4 for cocaine dependence. <i>Conclusions:</i> The study gives further support to SDS dimensional properties and to its validity for rapid assessment of current heroin and cocaine dependence.