Objectives: This study was conducted to determine the extent of loneliness and effective factors in alcohol and drug dependence. Methods: A descriptive study was carried out between April - September 2008 in Ege University Medical Faculty Hospital, Department of Psychiatry Clinic, Alcohol and Drug Dependency Unit with 200 patients who accepted to join the research. The research data were collected with a descriptive information form and the UCLA Loneliness Scale. The data were analyzed by ANOVA and t-test. Results: The mean age of the alcohol- and drug-dependent patients was 39.55±12.86 years. It was determined that 79% of the patients were male, 58% were married, 49% had graduated from high school, 58% were employed, 66% perceived their income as moderate level, 89.5% had social security, and 84.5% of the dependent patients lived in a nuclear family. When we investigated the loneliness characteristics in this patient group, it was found that 71% of them had experienced loneliness, 35.9% experienced loneliness often, and 27.5% spent their leisure time involved with cultural/arts and intellectual activities. The mean loneliness scale score was 38.51±14.39, and marriage status, education level, perceived income level, and family type affected the loneliness scale mean score (p<0.05). Conclusion: It has been suggested that because of the Turkish family type and social support available to alcohol- or drug-dependent individuals, the loneliness score was determined to be low.