Executive tasks are important instruments for neuropsychological and cognitive research, but only a limited number of studies have investigated the test–retest reliability of these tasks. Such information is needed for optimizing task usage, for example, in longitudinal and intervention studies. In this study with healthy adults, we investigated the temporal stability of five executive tasks: the Simon task, a visuoverbal N-back task, a visuospatial N-back task, a running memory task, and the Number–letter task. These five tasks are frequently used in research, but previously published reliability data is very limited or totally lacking. The results from the present study showed considerable variability with the highest test–retest reliabilities amongst the three working memory tasks. Furthermore, reaction time measures indicated practice effects between the two sessions across the tasks. The present results set constraints to the interpretation of the results of longitudinal and intervention studies using these tasks.