While current models of mindfulness propose benefits to the executive functions of inhibition, updating and shifting through mindful breathing meditations, empirical findings on the effects of short mindful breathing meditations are inconclusive regarding their specificity and dose-response relations. Therefore, we compared short mindful breathing meditations (Experiment 1, 45 min over three sessions; Experiment 2, 80 min over four sessions) with relaxation trainings (progressive muscle relaxation; active control) and listening to podcasts (passive control) in two randomized controlled double-blinded trials. Reaction time tasks were used to assess the executive functions of updating (N-Back), inhibition (CPT-II), and shifting (Number-Letter Task). Results of both experiments suggest no mindfulness-specific improvements in executive functions. We conclude that effects following the first stages of mindfulness training may not be specific to the practice or too transient to be reliably measured in pre-post intervention designs. Implications for research in the field are discussed.