Service discovery is a critical element to the success of ad hoc computing. The traditional approaches of service discovery in wired networks are not directly applicable to ad hoc environment due to the inherent network dynamics and unstable connectivity. Contexts capture the current physical and virtual environment that uncovers the needs of user. This paper discusses the contexts that are important for service node in service provision, and client node in service acquisition. A new context-aware service discovery mechanism is proposed that exploits contexts to improve the current ad hoc service discovery techniques.