Location-Based Spatial Queries (LBSQ) are becoming more and more useful in location-based services such as those provided by cell-phones, Wireless LAN and GPS technologies. They support the access to information resources by taking into account the spatial context of the user when submitting the query, and the spatial location of the searched resources (instances). In fact, in a LBSQ the key-selection condition is generally a constraint on the distance of the resources in the database (instances) from the user location. One deficiency of current approaches is the fact that they do not manage the uncertainty that often characterizes the knowledge of either the user location or the searched instances. A model for representing and evaluating uncertain Location-Based Spatial Queries is proposed in which besides location uncertainty also the spatial condition can be imprecise. A two-step evaluation procedure of LBSQs is outlined based on a filter and on a refinement phase.