Introduction and objective: Psychoactive substances intoxication among children and adolescents still poses a significant problem. Objective: The aim of the study was to assess paediatric patients intoxicated with psychoactive substances, who were admitted to a children’s hospital and their history of comorbidities. Materials and methods: This retrospective study assessed medical records of paediatric patients hospitalised in the Provincial Specialist Children’s Hospital in Olsztyn in the period from January 1, 2016 to December 31, 2018. The study included a group of 303 patients aged 0–18 years, diagnosed with intoxication with psychoactive substances. Results: In the analysed period, 303 paediatric patients were admitted due to intoxication with psychoactive substances, accounting for 0.45% of all hospitalised patients. The mean age of the patients was 14.83 ± 2.88 years. Among them there were 158 (52.15%) girls and 145 (47.85%) boys. Conclusions: Among children, poisoning occurs most often outside home (party, public place, plot, park). Medications and alcohol are the most common psychoactive substances used by adolescents. In the analysed period, poisonings in young people between 15 and 16 years of age were most often caused by alcohol consumption, while poisoning with other psychoactive substances most often occurred between 17 and 18 years of age. Patients with one comorbid disease were found more likely to use psychoactive substances compared to others, while patients with more than one comorbid disease use psychoactive substances and mixed drugs. Patients without comorbidities are more likely to consume alcohol.