With advancement in wireless technologies like development of Wireless Application Protocol and third generation mobile system that has many powerful capabilities like storage of small database, query processing in mobile environment has become a hottest topic of research. Lot of research work is done on how to do efficient query processing in mobile environment taking into consideration the asymmetric features of mobile environment like low battery power, reduced communication bandwidth, frequent network disconnection. The query processing in a mobile environment involves join processing among different sites which include servers and mobile computers. Because of the presence of asymmetric features in a mobile computing environment and also the need for energy saving, the conventional distributed query processing cannot be directly applied to a mobile computing system. Now with advent of location based services and GPS enabled mobile devices different types of queries to obtain location based information has evolved in mobile environment like location dependent queries, location aware queries etc. Processing of such queries is another area of research. This paper deals with the mobile query processing with special focus on classification of mobile queries and issues in mobile query processing.