Abstract. The aim of this study was to analyze the psychometric properties of the Questionnaire about Interpersonal Difficulties for Adolescents (QIDA; Inglés, Méndez, & Hidalgo, 2000 ). In Study 1, the questionnaire was administered to a sample of 4,240 high school pupils. Exploratory factor analysis identified five factors accounting for 42.86% of the variance: Assertiveness, Heterosexual Relationships, Public Speaking, Family Relationships, and Close Friendships. Internal consistency was high (.90). In Study 2, 538 high school pupils answered a set of social anxiety and personality self-report measures. Test-retest reliability, over a 2-week period, was adequate (.78). Correlations between the QIDA and the Personal Report of Confidence as Speaker (r = .43), the Social Phobia and Anxiety Inventory (r = .61), and the Eysenck Personality Questionnaire (r = -.38, Extraversion; r = .34, Neuroticism) were statistically significant. A significant difference was found between the total QIDA score for adolescents with and without social phobia (d = 1.53) supporting the construct validity of the questionnaire.