Background: These studies sought to investigate the relation between social desirability and self-reported health risk behaviors (e. g., alcohol use, drug use, smoking) in web-based research. Methods: Three longitudinal studies (Study 1: N = 5612, 51% women; Study 2: N = 619, 60%; Study 3: N = 846, 59%) among randomly selected members of two online panels (Dutch; German) using several social desirability measures (Marlowe-Crowne Scale; Balanced Inventory of Desirable Responding; The Social Desirability Scale-17) were conducted. Results: Social desirability was not associated with self-reported current behavior or behavior frequency. Sociodemographics (age; sex; education) did not moderate the effect of social desirability on self-reported measures regarding health risk behaviors. Conclusions: The studies at hand provided no convincing evidence to throw doubt on the usefulness of the Internet as a medium to collect self-reports on health risk behaviors.