Next generation networks are commonly associated with open service creation environments such as OSA, Parlay or JAIN. These environments make the capabilities provided by telecommunication networks accessible to third party application developers in a distributed way. Although the service capability descriptions currently proposed are appropriate for modelling static network elements some limitations are encountered when trying to use them in ad hoc networks. In this paper we propose a general service model for open service creation in ad hoc pervasive environments. The model proposed decomposes the service capabilities into a layered architecture that is well suited for dynamic service discovery and customization. KEYWORDS Ad-hoc networks, service creation model, pervasive computing, next generation networks.