The aim of this paper was to investigate habits of the use of nicotine products, alcohol and illicit drugs among people with and without ADHD. In the focus of this paper are the adults who are devided into three groups, persons with diagnosis of ADHD, persons without the diagnosis and persons with the expressed symptoms of ADHD. The participants (N = 199) have completed online questionnaire which consisted of the newly constructed questionnaire about the consumption of the psychoactive substances and the ASRS scale for the self-assessment for symptoms of ADHD. The questionnaire about the consumption of the psychoactive substances investigated habits of nicotine use, alcohol use and the use of illicit drugs. Quantitative approach was used for the data analysis. The results show that the differences between the three groups of participants are not statistically significant when it comes to the use of nicotine, as well as the unsuccessful cessation of smoking. Almost all participants have tried some nicotine products and about half of them smoke. There are no statistically significant differences when it comes to the use of alcohol and the regular use of alcohol, among the three groups of participants. The differences are not significant when it comes to excessive dringkin („binge drinking“), but it is visible that almost one third of participants drinks in this way, and almost all participants have tried alcohol at least once. But there are statistically significant differences when it comes to the feeling of wanting or needing alcohol. The participants without the diagnosis wanted or felt the need for the alcohol significantly more than the participants of the other two groups. There are statistically significant differences in the measure of the use of the illicit drugs and the measure of the regular use of the illicit drugs. The participants with the diagnosis and the participants with expressed symptoms use illicit drugs significantly more than the participants without the diagnosis. The results of this study should be interpreted carefully, taking into consideration its limitations. This study can be used as a way to lead the experts to think about this issue, in the science and research, as well as in the everyday practical work with the people with ADHD. It could also encourage more efficient prevention programs.