This study compared behavioural, cognitive, and motivational components of religiosity among 54 Jewish adolescents (aged 13-21 years) and 35 adults (aged 30-60 years) with intellectual disability (ID) (IQ=40-69). A special questionnaire was constructed based on several previous studies by other authors. A different pattern was found between age groups. The adolescents fulfilled Jewish commandments to a greater extent than the adults. Social psychology theories regarding religion change/stability over the lifecycle can serve as an explanation for these findings. The cognitive component was measured using a Piagetean-type scale. The scores in prayer efficacy and providence of God were significantly higher among the adults than among the adolescents. The adults also exhibited more mature motives of fulfilling commandments (dependence on God) than the adolescents. Regression analysis indicated that among the adolescents, mental age contributed to the explained variance of the behavioural and cognitive components, while among the adults chronological age contributed to the explained variance of these components. (Contains 8 tables.)