Mobile database applications through wireless equipments e.g., PDAs, laptops, cell phones and etc. are growing rapidly. In such environment, clients, servers and object may change their locations. A very applicable class of query is continuous k-NN query which continuously returns the k nearest objects to the current location of the requester. Respect to limitations in mobile environments, it is strongly recommended to minimize number of connections and volume of data transmission from the servers. Caching seems to be very profitable in such situations.