Results indicated that the upward trend in psychoactive substance use among teenagers documented in this study in the early and mid-1900s in Warsaw noted significant increase in youth substance use, including alcohol, cigarettes and illegal drugs; this may have been a response to the socioeconomic transition in Poland connected with both economic and cultural factors. Economic changes, especially privatization processes, have brought a rapid increase in availability of all substances both legal and illegal. The most recent results from 2000 to 2004 indicated stabilization in alcohol and illegal drug use and decrease in tobacco use. The trend in use of tranquillizers and sleeping pills was relatively stable over the past 16 years. Changes in adolescent substance use differ across gender. Findings suggest that during transformation, trends and patterns of substance use among Warsaw 15-year-old youth were similar to trends and patterns observed in some Western European countries. Research observations over almost 20 years, and changes to Warsaw youth substance-related behaviors serve to anticipate approaching changes among all youth in Poland. It is noteworthy that trends and patterns in youth substance use documented by nationwide studies are slightly different than those found in a big city such as Warsaw. Between 1988 and 2004, data were collected in six study waves utilizing the same procedure and instruments and targeted at 15-year-old students located in three districts of Warsaw. Tables, figure, and references