Working memory can be divided into three phases: encoding, maintenance, and retrieval. These phases have been studied on a neural level by observing the related oscillations. However, the roles of different oscillations in working memory processes remain partly unclear. The aim of this study was to examine oscillations related to encoding and maintenance and the inhibition of a distractor by comparing the brain activity during successful and unsuccessful trials during a visual working memory task. The study was conducted as a part of the WM-Inhibition-MEG project. Ten participants, aged 19-28, took part in the experiment. The experimental paradigm consisted of trials with facial images, and each trial consisted of three images: an encoder, a distractor, and a target image. The participants’ task was to compare the target image to the previously shown encoder image and indicate with a button press whether the images were the same or different. The measurements were recorded using magnetoencephalography and the data was analysed using time-frequency analysis method. We observed differences between successful and unsuccessful trials. There was less power in theta-alpha frequency band within the left temporal and occipital lobes during successful trials during maintenance before distractor stimulus. Immediately after the distractor stimulus we observed greater alpha power in the left frontal lobe during successful trials. This was most likely related to inhibition. In addition, we observed less beta band power in the right temporal and occipital lobes during successful trials. The results indicate that there are differences between successful and unsuccessful trials which can be observed within the oscillatory functions of the brain. This research serves as a starting point for more extensive research on the role of neural oscillations in successful working memory functions.