<p>The spectrum hypothesis posits that problematic online behaviors (POBs) are interrelated yet distinct. However, existing network analyses have focused on a narrow set of POBs, neglecting emerging behaviors and sex-related differences in the POB network. This study aimed to validate the spectrum hypothesis with seven POBs, test the hypothesized centrality of smartphone use, and examine sex-related differences in the POB network among Chinese adolescents. In a cross-sectional survey of 13,581 Chinese adolescents aged 15–20, we assessed seven POBs: problematic use of smartphones (PUS), social networking (PUSN), video gaming (PUVG), short videos (PUSV), internet novels (PUIN), online shopping (POS), and internet pornography (PUIP). Network analysis was used to estimate the symptom-level network structure, identify core and bridge symptoms, and compare networks between males and females. The network was stable and exhibited a clear community structure, with symptoms clustering into seven distinct domains corresponding to the seven POBs, supporting the spectrum hypothesis. Bridge centrality analysis revealed that symptoms of PUSV and PUSN were the most central bridges connecting different POB communities. For sex differences, the network structure significantly differed between males and females, but no differences were found in global strength or specific centrality indices. This study underscores the necessity of considering specific POB types in adolescents. Findings suggest that interventions should target content-specific bridging symptoms, particularly those related to PUSV and PUSN, and adopt sex-sensitive strategies. These insights call for clinicians, educators, and policymakers to address the spectrum of problematic online behaviors.</p>