The main objective of this chapter is to present a general overview of existing approaches on query processing and the authors’ vision on query evaluation in pervasive environments. It illustrates, with scenarios and practical examples, existing data and streams querying systems in pervasive environments. It describes the evaluation process of (i) mobile queries and queries on moving objects, (ii) continuous queries and (iii) stream queries. Finally, the chapter introduces the authors’ vision of query processing as a service composition in pervasive environments.