Patients with medication-overuse headache (MOH) and chronic migraine (CM) have varying degrees of addiction to painkillers (PK), which complicates treatment and leads to relapses. Development of addiction to PK is associated with various clinical and psychological characteristics and disorders in patients with MOH.Objective: to investigate the relationship between PK addiction and individual clinical and psychological characteristics in patients with CM and MOH.Material and methods. The study included 156 patients with CM and MOH (61 men and 95 women, mean age 34.1±8.9 years). Clinical and psychological characteristics were assessed in all patients using a clinical interview, tests and headache diaries. The relationship between PK addiction (according to the Leeds Dependence Questionnaire – LDQ) and clinical and psychological characteristics (duration of migraine and CM, frequency and intensity of headaches, duration of MOH, frequency of PK use, number of PK doses, personal and situational anxiety, depression, pain catastrophizing, beliefs about the body and health, coping strategies for stressful situations, daily activities during headache, insomnia) was investigated using regression analysis.Results. All patients had misconceptions and wrong behavior regarding PK. The majority (59%) of patients had moderate degree of PK addiction according to the LDQ. Twenty six percent of patients had other forms of addictive behavior (smoking, excessive alcohol consumption, overeating, excessive use of sleeping pills), and 52.6% of patients had relatives with addictive behavior. There was a statistically significantly positive correlation (R≥0.45; p<0.05) between PK addiction and smoking, alcohol consumption, use of sleeping pills, body mass index (BMI), frequency of PK use, attitudes towards pain, body and health (pain catastrophizing, hopelessness about pain, intolerance of body sensations, overestimation of symptom severity, catastrophizing in the interpretation of body symptoms), depression, personal anxiety and avoidance (maladaptive coping behavior). Adequate treatment of CM and MOH was provided in only 7.7% of patients.Conclusion: A positive association was found between PK addiction and smoking, alcohol consumption, use of sleeping pills, BMI, frequency of PK usage, attitudes towards pain, body and health, depression, personal anxiety and avoidance behavior.