With the global penetration of Internet technologies, individuals may now cross organizational boundaries to communicate efficiently with others regardless of time and space. Thus, when looking for help in solving work tasks, knowledge workers may just as easily contact individuals in rival firms across the globe as a coworker sitting at the next desk. As a result, management faces questions such as (1) How should firms manage employees' knowledge-sourcing activities when they span both intra-organizational and extra-organizational boundaries, and (2) What is the relationship between different knowledge-sourcing activities and individual performance? Grounded in the knowledge-based view of the firm, we investigate these questions using data from Europe's largest information technology (IT) services and management consulting company. Our results provide evidence that organizations should support boundary spanning and knowledge sourcing from both internal and external sources. Results suggest (1) a positive relationship between boundary spanning communication and creativity and general performance, and (2) a negative relationship between a reliance on colocated coworkers as knowledge sources and creativity.