Panel conditioning arises if respondents are influenced by participation in previous surveys, such that their answers differ from the answers of individuals who are interviewed for the first time. Having two panels - a trained one and a completely fresh one - created a unique opportunity for analyzing panel conditioning effects. To determine which type of question is sensitive to panel conditioning, 981 trained respondents and 2809 fresh respondents answered nine questions with different question types. The results in this paper show that panel conditioning mainly arises in knowledge questions. Answers to questions on attitudes, actual behavior, or facts were hardly sensitive to panel conditioning. The effect of panel conditioning in knowledge questions was bigger for questions where fewer respondents knew the answer and mainly associated with the number of times a respondent answered the exact same question before.