The aim of this study was to conduct a validation and assess the test–retest reliability of the health questionnaire based on Nordenfelt’s Welfare Theory of Health (WTH). The study used a questionnaire on health together with the Short Form 12-Item Health Survey (SF-12) questionnaire, and 490 pupils at colleges for adult education participated. The results of the study are in accordance with Nordenfelt’s WTH. Three hypotheses were stated, and the first was confirmed: People who were satisfied with life rated higher levels than those who were dissatisfied with life concerning both mental and physical health, measured with the SF-12. The second hypothesis was partially confirmed: People with high education were more often satisfied with life than those with low education, but they were not healthier. The third hypothesis, that women are unhealthy more often than men, was not confirmed. The questionnaire on health showed acceptable stability.