Many mobile phones have a GPS sensor that can report accurate location. Thus, if these location data are not protected adequately, they may cause privacy breeches. Moreover, several reports are available where persons have been stalked through GPS. The contributions of this paper are in two folds. First, we examine privacy issues in snapshot queries, and present our work and results in this area. The proposed method can guarantee that all queries are protected, while previously proposed algorithms only achieve a low success rate in some situations. Next, we discuss continuous queries and illustrate that current snapshot solutions cannot be applied to continuous queries. Then, we present results for our robust models for continuous queries. We will introduce a novel suite of algorithms called MobiPriv that addressed the shortcomings of previous work in location and query privacy in mobile systems. We evaluated the efficiency and effectiveness of the MobiPriv scheme against previously proposed anonymization approaches. For our experiments, we utilized real world traffic volume data, real world road network and mobile users generated realistically by a mobile object generator.