Adding location-awareness to publish-subscribe middleware infrastructures would open-up new opportunities to use this technology in the hot area of mobile applications. On the other hand, this requires to radically change the way published events are matched against received subscriptions. In this paper we examine this issue in detail and we present CLCB, a new algorithm using CUDA GPUs for massively parallel, high-performance, location-aware publish-subscribe matching and its implementation into a matching component that allows to easily build a full-fledged middleware system. A comparison with the state-of-the-art in this area shows the impressive increment in performance that GPUs may enable, even in this domain. At the same time, our performance analysis allows to identify those peculiar aspects of GPU programming that mostly impact the performance of this kind of algorithm.