As the penetration of the Internet into people's lives has increased, there is needed to rethink the diagnostic tools used to diagnose Internet addiction. The very concept of Internet addiction also needs to be rethought, as it currently reflects not the content but the form of addiction. The aim of the work was to develop, evaluate psychometric reliability and validate a new diagnostic instrument for the cyberaddiction diagnosis. The proposed “Yuryeva — Shornikov Cyberaddiction Scale” (YSCAS) consists of 18 statements that are rated on a 5-point Likert scale. The study included 217 people (151 women) aged 19 to 69 years. At the first stage, the internal consistency of the YSCAS scale, external and content validity were assessed, at the second stage we assess stability, constructive and criterial validity. In assessing the internal consistency and homogeneity scale YSCAS Cronbach alpha was 0.84. There is proved the absence of gender influence on the indicators of the proposed scale. Spearman's correlation coefficient between YSCAS and Chen's Internet dependence scale was 0.8044 (p < 0.001), which indicates a high criterial validity. Assessing the constructive validity of the proposed scale, it was found that the YSCAS scale should be considered as a single factor scale, without sub-scales in its structure. The proposed cyberaddiction diagnosing method showed a high-quality prognostic model using ROC analysis: the area under the curve (AUC) was 0.971 (95 % CI 0.88; 1.0). The sensitivity of the scale was 100.0 % with a specificity of 90.4 %. As a result of approbation of the proposed psychodiagnostics method “Yuryeva — Shornikov Cyberaddiction Scale”, it was found that this scale is a reliable and credible approach to diagnose cyberaddiction.