Internet addiction has been found to be prevalent worldwide, including Asian countries, and related to several negative outcomes and other behavioral addictions. The Bergen Social Media Addiction Scale (BSMAS), Smartphone Application-Based Addiction Scale (SABAS), and nine-item Internet Gaming Disorder Scale-Short Form (IGDS-SF9) have been extensively used to assess internet-related addictions. However, the three aforementioned instruments have rarely been used in Asian countries. The aim of the present study was to investigate whether the BSMAS, SABAS, and IGDS-SF9 were appropriate for use in heterogeneous subsamples from Hong Kong and Taiwan. University students from Hong Kong (n = 306) and Taiwan (n = 336) were recruited via an online survey. Multigroup confirmatory factor analysis (MGCFA) was used to assess measurement invariance of the BSMAS, SABAS, and IGDS-SF9 across the two subcultures. The original unidimensional structures of BSMAS, SABAS and IGDS-SF9 were confirmed through confirmatory factorial analysis in both subcultures. The MGCFA results showed that the unidimensional structures of the BSMAS and IGDS-SF9 were invariant across the two Chinese cultural areas (Hong Kong and Taiwan). However, the measurement invariance of the SABAS was established after some model modifications. In conclusion, the present study found that the Chinese BSMAS, SABAS, and IGDS-SF9 were all adequate instruments to validly assess internet-related addictions among university students. The three brief instruments used for assessing addictions to social media, smartphone applications, and online gaming are valid and psychometrically robust across two Chinese subcultures and can be used by healthcare professionals in these regions.