Location-based services (LBS) are information and entertainment services which are accessible from the mobile device through the mobile network based on the geographical position of the mobile device at the time of request. LBS are an abstraction of spatial queries, e.g., range and k-nearest-neighbor (k-NN) queries. Due to the spatial locality of LBS, a lot of recent research has shown that peer-to-peer (P2P) cooperation is an effective and efficient technique to improve the performance of LBS systems. With the new IEEE standardization of Dedicated Short Range Communication (DSRC)/ Wireless Access in Vehicular Environments (WAVE), Vehicular Ad Hoc Networks (VANETs) which are designed for data exchange between high-speed vehicles and between the roadside infrastructure and the vehicle have recently reemerged as a promising mobile computing platform. Both LBS and VANETs have been well studied, but most existing VANET-based LBS only support simple information dissemination applications. It becomes a very timely topic to develop a new VANET-based framework to support spatial queries. VANETs have many unique characteristics compared to mobile ad hoc networks (MANETs) including road network constraints, mobility prediction, frequent disconnection and ample energy and capacity. These key characteristics make existing MANETbased LBS frameworks not suitable for high-speed vehicles. In this thesis, we investigate the above unique characteristics of VANETs. A comprehensive survey of mobile peer-to-peer data dissemination and query processing is presented. According to the characteristics and the present works, we discuss some open challenges in VANET-based LBS. Specifically, to better understand the access between vehicles and roadside units, an analytical study on cooperative data dissemination in push-based mobile P2P networks is conducted. We propose a spatial query processing framework with cooperative data dissemination in VANETs. In the proposed k-NN query processing framework, we design the road-based semantic caching, statistics-based query time-to-live estimation, and hybrid routing techniques to enable k-NN query processing in VANETs. Based on this framework, road-side units (RSUs) are utilized as an infrastructure support to facilitate spatial query processing with cooperative data dissemination in VANETs. Besides, we propose the cache sharing optimization for cooperative data dissemination in VANETs. Experiment results show that cooperative data dissemination techniques such as vehicle-roadside access and cache sharing significantly improve the system performance in terms of query response time, answer accuracy and communication overhead.