Abstract: In this study, we divided adaptive resources allocation for multiuser OFDM system into two continuous parts: (1) subcarrier allocation and (2) power allocation and proposed a modified particle swarm optimization (PSO and GA) to deal with this adaptive resources allocation for multiuser OFDM system in three main scenarios: (1) multiuser unicast services; (2) multiuser multicast services at low and constant rate and (3) multiuser multicast services at high rate. Simulation results show that adaptive resources allocation for multiuser OFDM system can be done by normal PSO and modified PSO in these three scenarios. Comparing the allocation scheme of both algorithms, this modified PSO (PSO and GA) can greatly improve performance of adaptive resources allocations.