Abstract. Caching can highly improve performance of query processing in distributed databases. In this paper we show how this technique can be used in grid architecture where data integration is implemented by means of updatable views. Views integrate data from heterogeneous sources and provide users with their integrated form. The whole process of integration is transparent, i.e. users need not be aware that data are not located at one place. In data grids caching can be used at different levels of architecture. We focus on caching at the middleware layer where the cache is stored in the database of the integrating unit. These results can be then used while answering queries from grid users, so there will be no need to reevaluate the whole queries. In such a way caching can highly increase performance of applications operating on grid. In the paper we also present an example how a query can be optimized by rewriting to make use of cached results.