Working memory capacity (WMC) is important for many cognitive processes including problem solving. This chapter compiles the current literature regarding WMC and problem solving, and discusses the various ways in which WMC can help and hinder people as they go about solving problems of varying types. In particular, three types of problem solving are examined: mathematical problem solving, problem solving as it relates to the Raven Progressive Matrices (RPM), and creative problem solving. One of the main benefits across both math and RPM problem solving seems to be that WMC helps solvers to focus their attention, resist distraction, or narrow their search through a problem space. Conversely, several lines of evidence are now showing that too much focus can actually harm performance on creative or insightful problem-solving tasks. It is suggested that in order to account for the differing relationships between WMC and different types of problem solving, a dual-process, analytical/insightful model of problem solving is required.