Among the emerging investigative fields, forensic medicine and toxicology lead to analyzing fatalities in medico-legal expert opinion formulating. While discussing the problem, the authors have selected 96 fatal cases from their expert practice including the period from 2010 to 2023, in which deaths were connected with taking new psychoactive substances (NPS’s) belonging to various chemical categories, mainly synthetic cathinones (SC), synthetic cannabinoids (SCan) and non-medical synthetic opioids (NSO). In the investigated cases, toxicological analysis revealed 37 NPS’s and their 9 metabolites. The cases involved the use of SC’s (64 cases - 67 %), Scan’s, including their metabolites (10 cases - 10 %) and NSO’s, including their metabolites (6 cases - 6 %). The remaining cases involved the simultaneous use of NSO with SC and/or SCan, including their metabolites (8 cases - 8 %), or SC with SCan (5 cases - 5 %). In three cases (3 %), compounds belonging to other groups were taken. In twenty-five cases, more than one NPS was found. Moreover, in twenty-seven cases, ethyl alcohol was also detected at the concentration range of 0.6–3.6 ‰. The concentration of xenobiotics determined in blood represented extensive ranges of concentration. The victims were at the age of 16–58 years of life. The group included eleven women (11 %). Generally, the deaths related to NPS’s were predominantly of an accidental character (81 %), while the manner of death in sixteen cases (17 %) was suicide, including hanging (5 cases), jumping from a great height (3 cases), self-injury and exsanguination (1 case), as well as acute drug intoxication (6 cases) and intoxication with central nervous system hypoxia after an hanging (1 case). Among the analyzed cases there were two victims of homicide (2 %), in one of which the perpetrator being under the influence of the mixture of the synthetic opioid U-47700 and synthetic cannabinoid AB-FUBINACA. In twenty-eight cases, medications used in psychiatry were found, which suggested that the victims were struggling with mental problems before death. As it was implied by the available information, more than 36 % of the victims had mental problems.