In this paper, a problem for efficient use of subcarriers in downlink OFDMA multi-hop cellular networks is studied based on quality of service (QoS) guarantee of each mobile station (MS). We consider three possible transmission schemes in multihop networks: single-hop, multi-hop, and multi-hop with spatial reuse of subcarriers. We verify that the required number of subcarriers to guarantee the target BER and the target data rate is changed according to the transmission scheme and QoS requirements as well as the channel condition. Based on this result, we propose a new transmission scheme selection algorithm to select the best performance scheme for the efficient utilization of the limited subcarriers. Through the numerical results, the performance of this algorithm is demonstrated by the number of supported MSs in the system and the blocking probability.