Objectives:
The use of the novel psychoactive substances (NPS) is a relatively new phenomenon on the Polish drug scene. At the same time, it is rapidly growing group of substances. The aim of the article is to present the negative consequences to physical, mental and social health due to novel psychoactive substances use.

Methods:
Fieldwork was conducted in 2016 in four locations: Warsaw, Krakow, Poznan, and Tri-City. A total of 596 users of novel psychoactive substances participated in the study. Among them were: nightlife users (N = 172), marginalised users (N = 86) and users active on the internet (N = 338). A self-administered questionnaire was used.

Results:
The substances from the stimulant/empathogen/nootropics group were the most commonly used among nightlife users, marginalised users and users active on the internet. The herbal blends were less popular, and the synthetic cannabinoids appeared on the third position. The acute side effects were most common consequences. Prevalence of medium- and long-termproblems withmentaland physicalhealth as well as social problems was at a similar level. All types of negative consequences were most prevalent among marginalised users.

Conclusions:
Novel psychoactive substances users experience several negative consequences. This poses a challenge to the treatment services that must answer with adequate form of help. This is not easy due to diagnostic difficulties as the effects of NPS use are often indistinguishable to the symptoms of the traditional drugs. Thus, there is a need for further research, which would allow to observe and closely monitor the problem.