Abstract. Addictions to alcohol and drugs are associated with impairments in various domains of cognitive functioning. The aim of the present research is to investigate the psychometric properties of the Letter Cancellation test and its potential to discriminate different degrees of impairment in functions of attention among addicts. The study was conducted among 270 adults aged above 18 years in Sofia, Bulgaria, and included treatment and control groups. The treatment group (TG) consists of 99 men and 36 women dependent on alcohol or drugs (included in substitution treatment or psychosocial rehabilitation programs). The control group (CG) is balanced by gender and age with the TG. For the purpose of the study, a modification of the Letter Cancellation test is used. The results confirmed the ability of the method to measure different functions of attention. Addicts performed significantly worse on tasks measuring functions of attention in comparison to the CG. Alcohol addicts have significantly worse performance on all examined functions of attention (focus, sustainability, division, and switching), and drug addicts enrolled from methadone maintenance treatment programs have significantly poorer ability to focus and sustain their attention in comparison to individuals from the CG. Drug addicts enrolled from programs for psychosocial rehabilitation performed similarly to CG. These results confirm the validity and reliability of the method for assessment of the functions of attention in individuals with substance use disorders and its applicability for refining treatment, rehabilitation, and re-socialization of addicts.

Key words: functions of attention, focus of attention, sustained attention, divided attention, switching attention, alcohol and drug addictions

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