The present study investigated the differences in learning gain when performing a WebQuest with a well-defined versus an ill-defined assignment. Twenty boys and twenty girls (mean age 11; 10), attending a special primary education school, performed two WebQuests. In each WebQuest, they performed either a well-defined or an ill-defined assignment. Knowledge acquisition was assessed by means of a concept map (ie, associative knowledge) and a knowledge test, based on facts concerning the subject (ie, factual knowledge). Results indicated that the learning gain on both WebQuests was higher for participants who worked on the ill-defined assignments. In the long term, factual knowledge remained intact. The results of this study indicated that the use of WebQuest can be a valuable tool to enrich the educational curriculum in special education.