Abstract Background In recent years, researchers have begun to explore the implications of shyness for the psychosocial wellbeing of children and adolescents, exploring its association with internalizing problems. Research in an Italian context is hindered by the lack of a validated self-report measure of shyness. We report two studies aimed to assess the psychometric properties of an Italian translation of the Children’s Shyness Questionnaire (CSQ-it) and investigate its correlations with convergent and divergent constructs. The first study aimed to examine associations between CSQ-it and self-report measures of anxiety and somatic symptoms and attachment with parents and peers. The second study aimed to investigate its relations to internet addiction. Methods The self-report measures were completed by 550 participants in the first study and 131 participants in the second study. Parents provided information on their child’s problems. Psychometric properties were assessed by Cronbach’s alpha in both studies and by exploratory and confirmatory factor analysis in Study 1. The relations between shyness and measures of internalizing problems and attachments were analyzed by correlational methods. In Study 2 a moderated mediation model tested the hypothesis that the relationship between shyness and internet addiction is mediated by somatic symptoms and that shyness moderates the relationship between somatic symptoms and internet addiction. Results The reliability and validity of the Italian Version of the Children’s Shyness Questionnaire were satisfactory. Results from confirmatory factor analyses confirmed the single-factor model of the questionnaire previously identified in North American and Chinese studies. There were significant correlations between shyness, anxious and somatic symptomatology, impaired psychosocial functioning and specific components of attachment relationships. In Study 2 the indirect effect of shyness on internet addiction through somatic symptoms was significant as well as significantly moderated for high shyness scores but not for low levels of shyness. Conclusion To our knowledge this is the first study that explored the psychometric proprieties of the Children’s Shyness Questionnaire in the Italian context. Findings demonstrated that this self-reported measure of shyness has sound psychometric properties and can be used as a sensitive and appropriate instrument for the assessment of shyness in children and adolescents.