Introduction:
Comparisons between the epidemiological data originating from different countries are the basis for understanding the changes taking place in the world. We should always consider whether comparing the consumption of psychoactive substances in the two different populations enables us to draw objective conclusions.

Aim:
The main aim of this article is to assess the ability to compare the results of studies about the usage of psychoactive substances in Poland and the United States from a methodological point of view.

Material and Methods:
Those issues are based on national researches undertaken in Poland and the United States. Standardization of the data, weighting the sample, selection of respondents and choice of the standard population were analyzed. Items were evaluated that showed significant differences between the studies on consumption of psychoactive substances in Poland and the United States.

Results:
Analysis of many factors which are the cause of emerging gaps between researches, have revealed that, based on the available data, creating practical directives may be flawed, resulting from the significant differences between them. Knowledge about collecting and analyzing the data, choice of the standard population, weighting the data and legal or cultural predispositions, lead to the effective and objective comparison of the data.

Conclusions:
When accounting for the funds spent on the epidemiological studies conducted in Poland, mandatory reporting of survey methods and analysis of results should be imposed. This would allow for easier comparison of the drug abuse situation in Poland, compared with other countries.