Objectives The primary objective of this study was to compare the estimates of Problematic Internet Use (PIU) from 14 countries around the world, considering gender. The second objective was to explore the relationships between PIU and personality-related variables (pathological personality traits, defense mechanisms, coping strategies, and self-esteem). Materials and methods Our total sample consisted of 7726 participants (30.8% male, n = 2378), aged between 18 and 86 years old (M = 25.55; SD = 9.8). Recruited online, they completed several scales about their Internet use, defense mechanisms and coping strategies, self-esteem, and pathological personality traits. Results The PIU accounted for between 20.5% and 75% of participants using the PIUQ-9, while “self-perception” of PIU with a single item revealed estimates from 2% to 60.1%, with gender differences. Systematically, PIU significantly correlated with two variables: borderline personality traits (from .09 at P < .05 to .42 at P < .01) and immature defense mechanisms (from .13 to .42 at P < .01). Dependent, avoidant, narcissistic, histrionic, and antisocial personality traits were positive predictors of PIU and self-esteem, paranoid and schizoid personalities were negative predictors.