Making accurate judgments is an essential skill in everyday life. However, little is known about the basic cognitive skills required for accurate judgments. Research on judgment and categorization processes suggests that people rely on various strategies when making judgments. These strategies differ in the cognitive abilities they require. Specifically high working memory capacity may benefit rule-based judgments, whereas good long-term memory may be crucial for memory-based judgments. We investigated this hypothesis following an individual differences approach. 177 participants performed two judgment tasks that were either best solved by a rule-based or a memory-based strategy. Additionally, we measured working memory capacity and episodic memory with three tests. Consistent with our hypothesis structural equation modeling showed that working memory capacity predicted judgment accuracy in the rule-based task whereas episodic memory predicted judgment accuracy in the memory-based task. Apparently, different memory abilities are essential for successfully adopting different judgment strategies.