Recently, operators have resorted to femtocell networks to enhance indoor coverage and increase system capacity. Nevertheless, to successfully deploy such solution, efficient resource-allocation algorithms and interference mitigation techniques should be deployed. The new applications delivered by operators require large amounts of network bandwidth. Although, some customers may want to pay more in exchange for a better quality of service (QoS), some others need fewer resources and can be charged accordingly. Hence, we consider an orthogonal frequency-division multiple-access (OFDMA) femtocell network serving both QoS-constrained high-priority (HP) and best-effort (BE) users. Our objective is to satisfy a maximum number of HP users while serving BE users as well as possible. This multiobjective optimization problem is NP-hard. For this aim, we propose in this paper a new resource-allocation and admission control algorithm, which is called QoS-based femtocell resource allocation (Q-FCRA), based on clustering and taking into account QoS requirements. We show through extensive network simulations that our proposal outperforms two state-of-the-art schemes [centralized-dynamic frequency planning (C-DFP) and distributed random access (DRA)] and our previous proposal, i.e., femtocell resource allocation (FCRA), in both low- and high-density networks. The results concern the throughput satisfaction rate, spectrum spatial reuse, the rate of rejected users, fairness, and computation and convergence time.