An example from the statistical data collected by the Office of Health Statistics is showing the increase from 13 % in the year 1996 to 18 % in 2004 of the proportion of diagnosis encoded as “F1x.1” – harmful use of psychoactive substances according to ICD-10. Probable reason of this unusually large proportion of the diagnosis is an error in the official Slovak translation of the ICD-10 manual, where the term abuse is written incorrectly under the code “F1x.1”. This term has a wider meaning and in the American DSM-IV classification, which is not used by us, may encompass also behavioural manifestations, which are not associated with the impairment of health. Some of “Z” codes should be used instead in these cases in our practice according to ICD-10, which is designated for diagnostic processes to exclude mental or physical health impairments. Because this error can lead to negative consequences for the individual, the authors appeal to relevant institutions to make a correction as soon, as it is possible, and to inform the health workers about the necessity to change their current diagnostic practice.

Key words: harmful use – abuse – ICD-10