It is well known that WLAN based on the IEEE 802.11 standard suffers from interference and scalability problems due to a limited number of nonoverlappingchannels. In order to mitigate the interference problem, channel assignment algorithms have been a popular research topic in recent years. It has been shown that such algorithms can greatly reduce the interference amongwireless access points. However, in this paper we show that previously proposed channel assignment algorithms may lead to an increased number of hidden nodes in dense network deployments. We also show that this can significantly decrease the performance of the network. Furthermore, we present results from experiments showing that the RTS/CTS mechanism is unable to solve the hidden node problem in infrastructure WLANs and therefore, careful consideration needs to be taken when choosing channel assignment strategies in densely deployed wireless networks. To this end, we propose two novel channel assignment algorithms. Using a simulation study, we show that the proposed algorithms can outperform traditional channel assignment in densely deployed scenarios, in terms of QoS sensitive VoIP support without compromising the aggregate throughput and are therefore a better performing alternative in such settings.