During the COVID-19 pandemic, researchers recorded the growth of cyberchondria as a tendency to excessive and repetitive search on the Internet for information about the symptoms of various diseases. The objective of this study was to adapt the Russian version of the Cyberchondria Severity Scale-12 (CSS-12). It measures the structure of cyberchondria: compulsion, i.e. searching online interrupts daily activities; distress, i.e. the negative emotional consequences of the search behavior; excessiveness, i.e. repeated health-related research that may escalate search behavior; reassurance, i.e. desire to consult with a health care provider after searching online (McElroy, Shevlin, 2014). The cross-sectional study involved 624 respondents who completed the Russian-language versions of the CSS-12 and the Symptom Check List-90-Revised (SCL 90-R). The confirmatory factor analysis revealed the bifactor structure of the Russian CSS-12, suggesting both the general factor of cyberchondria and specific factors of excessiveness, distress, reassurance, and compulsion. The Russian CSS-12 demonstrated high internal reliability with an α-Cronbach coefficient of 0.95 for the total score. The convergent validity of the Russian CSS-12 was confirmed through its positive correlations with the SCL-90-R scores. Results of the sociodemographic analysis showed that cyberchondria was not associated with gender, but excessiveness, distress, reassurance, compulsions, and total CSS-12 score were negatively associated with age. The findings showed that the Russian CSS-12 is a reliable and valid instrument for population-based research of cyberchondria and needs further psychometric examination on various clinical samples.