Adequate ehealth literacy is one of the key instruments safeguarding people against unreliable health-related information obtained from the Internet. This paper presents an assessment of the reliability and the validity of a Polish version of the ehealth literacy scale (Pl-eHEALS). The assessment was carried out on the basis of two nationally representative samples of the Polish population. In the first survey of adults at least 50 years old, the technique of computer-assisted telephone interviewing (CATI) was applied. In the second survey of young adult women (18−35 years old), the technique of computer-assisted web interviewing (CAWI) was used. The reliability and the validity of the Pl-eHEALS was analyzed. There were no floor or ceiling effects revealed in either sample. The Cronbach’s alpha coefficients were 0.90 and 0.88, and Guttman split-half coefficients were 0.89 and 0.81, respectively. Exploratory factors analysis revealed single factor models in both cases. The sum of squared loadings in the first survey was 6.090 and accounted for 58.72% of the variance. In the second survey, the sum was 5.927 and was responsible for 55.06% of the variance. Hypothesis testing showed that, for older adults, higher ehealth literacy was prevalent in the respondents who used the Internet more frequently. Among young adult women, higher readiness to use the Internet as a primary source of health-related information and to undertake specific internet health-related activities was associated with higher ehealth literacy. The analysis reported in this paper confirmed the reliability and the validity of the instrument. It should be stressed that, prior to this study, there was no validated Polish version of the eHEALS that could be used with Polish-speaking respondents.