Effects of emotional content on working memory performance and the underlying neural mechanism were  explored in this study, with a time-locked delayed matching-to-sample task (DMST) and a high-temporal resolution  event-related potential (ERP) technique. Faster RTs and higher accuracy were observed in positive stimuli, while  slower RTs and lower accuracy in negative stimuli. At encoding, an enhanced anterior P2 component was elicited by  negative compared to neutral stimuli; at retention, the sustained slow wave (SW) showed a more positive deflection for  both positive and negative stimuli compared to neutral stimuli during early and middle periods; at retrieval, a significant  N400 old-new effect was observed and this effect for positive stimuli tended to be largest. The findings suggest that  positive stimuli enhance working memory performance by facilitating retention and retrieval processing, while negative  stimuli impede working memory performance as the negative emotion may be avoided during retrieval in spite of  privileged processing during previous encoding and retention. © 2013 Springer-Verlag.