Background and objectivesThe counter-app method is often used to assess the frequency of intrusions. The method requires the participants to press a button on a smartphone whenever an intrusion occurs during a predefined time period. We evaluated the convergent, discriminant, and predictive validity of the counter-app method in two studies. MethodsIn the first study, we assessed the frequency of intrusions with a counter-app method, thought-sampling method, and a retrospective measure in N = 77 students. Additionally, we assessed retrospectively-estimated duration, percentage of time, intensity, and intrusiveness of intrusions. The second study (N = 65) was identical to the first except the thinking-aloud method replaced the thought-sampling method, and additionally we assessed behavioral neutralizing. ResultsThe counter-app frequency was positively correlated with the convergent (thought-sampling and thinking-aloud frequencies, and retrospectively-estimated frequencies of intrusions) and predictive (behavioral neutralizing) validity criteria. The correlations between counter-app frequency and discriminant validity criteria (retrospectively-estimated duration, percentage of time, intensity, and intrusiveness of intrusions) were not smaller than the correlations between counter-app frequency and convergent validity criteria. LimitationsWe evaluated the predictive validity of the counter-app method using a criterion typical of obsessive-compulsive disorder research. Thus, the result for predictive validity might not transfer to other areas. ConclusionsOur findings support convergent and predictive, but not discriminant, validity of the counter-app method. The counter-app method can validly assess the frequency of intrusions but is not appropriate if the study requires the differentiation of frequency from other constructs such as duration.