Two studies examined shared and unique relations of social information processing (SIP) to youth's anxious and depressive symptoms. Whether SIP added unique variance over and above trait affect in predicting internalizing symptoms was also examined. In Study 1, 215 youth (ages 8-13) completed symptom measures of anxiety and depression and a vignette-based interview measure of SIP. Anxiety and depression were each related to a more negative information-processing style. Only depression was uniquely related to a less positive information processing style. In Study 2, 127 youth (ages 10-13) completed measures of anxiety, depression, SIP, and trait affect. SIP's relations to internalizing symptoms were replicated. Over and above negative affect, negative SIP predicted both anxiety and depression. Low positive SIP added variance over and above positive affect in predicting only depression. Finally, SIP functioning partially mediated the relations of affect to internalizing symptoms. (Contains 1 footnote, 2 tables and 1 figure.)