The case of the fifteen years old girl demonstrates the typical misdiagnosis of the fast deteriorating school results in elementary school children. In history of this patient, a dysfunctional family has been described. There has not been described any serious disease in the family history. The patient was born from the first physiological gravidity; she has never been seriously ill. She had behavioural problems since her attendance into kindergarten. In the 2nd class of elementary school, she started education at a special class for dyslectic children. During admission, the patient was unwilling to communicate; she was in full consciousness, slightly suppressed, highly dysphoric. She did not have any problem regarding receptivity and intellectual ability. She confessed to the abuse of many addictive substances. She has regularly used marihuana and alcohol from age 12, opioids, LSD and stimulant drugs from age 14, and heroin in daily dose of 0.2 g during the last two months. Her minimum opinion about the invalid condition and her uncritical relationship to the own behaviour were unalterable. As the Department of adolescent psychiatry has other therapeutic intention, she was transferred to the special department for the treatment of drug dependence with the diagnoses of dissocialised behavioural disorder (F 91.1) and drug dependence (F 19.1).

        Key words: school phobia, behavioural disorder, drug abuse, drug dependence