Emotion regulation (ER) plays an important role in everyday functioning. Maladaptive or ineffective ER strategies are associated with poor well-being and, in the worst case, with psychological disorders. Lower effectiveness of ER strategies could result from lower efficiency in their implementation. Extensive literature exists describing the time-course of emotion-related responding, but only few to no studies at all target ER efficiency. Therefore, the aim was to identify a measurement reflecting ER efficiency. Data sets from two independent studies were examined. In study one, N = 35 healthy participants completed an ER paradigm. While participants permitted or detached emotions during inspection of negative and neutral images in an event-related design, electroencephalography (EEG) was recorded. As expected, we observed a late positive potential (LPP) during inspection of negative images. The LPP was modulated by strategy use, however, LPP was greater while using detachment from emotions, compared to permission of emotions (i.e. ER was not successful). Due to difficulties with experimental design in study one, a second study was conducted. During inspection of positive and negative images participants should detach from or suppress their emotions. Each condition was performed in one block. After each block, participants rated their subjective efficiency during the use of the strategies. Ratings of subjective efficiency will be investigated with regard to their relationship to the objective measure. These findings will be discussed with regard to the question whether ER efficiency can be identified in EEG measures and its relation to ER effectiveness.