The prefrontal cortex (PFC) plays an important role in working memory [1], however, the underlying neural processes remains elusive. Studies on the hippocampus revealed that place cell sequences encode goal-directed behavior in rats [2]. In this study, we report about the existence of sequential activation patterns in PFC and their correlation with behavior in a working memory task. Experiments were conducted with one-photon calcium imaging in Thy1-GCaMP6f mice during an olfaction-guided spatial memory task in a three-arm arena consisting of sampling, choice, and reward conditions. In order to get the reward, animals had to learn to associate odorants presented in the middle arm to the reward location in the left or right arm. Calcium traces of PFC neurons from four animals were used for sequence analysis. Sequences were searched in activity bursts within 500 ms time windows. Applying a hierarchical clustering algorithm to the pair-wise order similarity matrix of sequences enabled us to categorize them into distinct clusters. We observed a significant shift in cluster distribution during sampling and reward periods post-learning, indicating dynamic changes in PFC sequence expression as the animal acquires the task. Additionally, we identified that an average of 16% of clusters encoded the animal's position within the maze, while 48% encoded the animal's distance to the reward site. Furthermore, among cells with significant spatial information, 44% were position-encoding, and 56% were target-encoding. These findings suggest that task-related place encoding in the PFC is driven by both the activity of individual cells and the coordinated co-activation patterns of cell groups. Our results show that one-photon recordings allow for the analysis of fast sequences in the PFC, revealing task phase-dependent differences in PFC sequences. These findings suggest a potential role of PFC sequential activation in working memory tasks and underscore the importance of investigating co-activation patterns of neural activity in the PFC.