OBJECTIVE: This study aims to explore the prevalence, characteristics, and psychopathology related to Problematic Use of Internet (PUI), including Internet Addiction (IA), within a sample of psychiatric outpatients. METHODS: 143 psychiatric stable outpatients (18-65, mean age: 49; F=84) were included in this study, regardless of their categorical diagnosis. Socio-demographic, clinical, psychopathological, and Internet use-related data (PIU-Scale, Internet Addiction Test, devices, use, activities) were collected across the sample. RESULTS: The prevalence of PUI ranged between 1% (IAT) and 25% (PIU-S), with a homogeneous distribution of PUI symptoms' severity among the four main psychopathological areas (depressive, bipolar, anxiety, and psychotic disorders). PUI was correlated with age and was higher in students as in the general population. Significant associations were found between PUI symptoms and both personality and eating disorders; PUI was also positively correlated with the presence of other addictions (e.g., alcohol and/or substances). A greater proportion of patients with PUI presented other forms of behavioural addiction compared to non-symptomatic patients. Social media and online shopping, as well as video-streaming, resulted to be the main forms of PUI among patients with problematic use of the Internet. DISCUSSION: More studies are required among students diagnosed with eating and personality disorders. The association between PUI and other addictive disorders would support the hypothesis of their common shared pathophysiology. CONCLUSION: Healthcare providers and educators should be made aware of such risks. More studies are needed to confirm such preliminary findings.