The present study examined the relationships among conditional inference, working memory (WM) and prepotent response inhibition (PRI) across different age groups. Participants (N = 112) of this study included preschoolers (6-year-olds), third graders (8-year-olds), fifth graders (11-year-olds) and eighth graders (13-year-olds). There were two conditional inference tasks, one based on a factual proposition and another based on a counterfactual proposition. The backward digit span task and Stroop task were used as the measures of WM and PRI, respectively. Results of the present study revealed that conditional inference was related to WM in all age groups, but was related to PRI in only the preschoolers, third graders and fifth graders. Data suggested that the role of WM and PRI varied with age development.