This paper deals with the topic of the impact of drug use on road traffic safety, and discusses in more detail the types of drugs, legislation, the situation in the Republic of Croatia and the prerequisites for traffic safety. Addiction is an impossibility without something or anyone; conditioning by which or dependence you do not be independent. It can be psychological or physiological in nature. Drugs are any substance of natural or artificial origin, including psychotropic substances, included in the list of drugs and psychotropic substances. Europeans spend about 30 billion euros each year on drugs, of which about 39% are on cannabis, 31% on cocaine, 25% on heroin and 5% on amphetamines and MDMA. The largest drug market in Europe is cannabis. In 2020, a total of 2,645 drug-related criminal offenses were reported in the Republic of Croatia. From 2005 to 2019, a total of 118 new psychoactive substances were identified in the Republic of Croatia (mostly synthetic cannabinoids and synthetic cathinones). Man's behavior directly affects on road traffic safety, and such behavior can be influenced by numerous factors (consumption of alcohol, drugs, medications, fatigue, etc.). Therefore, the most important thing is to take preventive action to avoid unwanted consequences. Man should act preventively on his own, but an important precondition for road traffic safety also applies to all stakeholders in the country. In other words, a stable system of organization of society is necessary. It is also of great importance to improve the structure of social intervention measures through road traffic safety action programs. The police also play a major role in preventing the misuse of narcotics in traffic, and they must constantly monitor the condition of drivers on the roads. Control as a preventive measure aims to keep the behavior of traffic participants within certain normatively permitted limits.