Abstract. For economic and efficient operation of power system optimal scheduling of generators to minimize fuel cost of generating units and its emission is a major consideration. This paper presents a new approach to Combined Economic and Emission Dispatch (CEED) problem having conflicting economic and emission objectives using a Hybrid Particle Swarm Optimization and Firefly (HPSOFF) algorithm. The CEED problem is therefore formulated as a multi-objective optimization problem with the valve point effect using a price based penalty factor method. The effectiveness of the proposed HPSOFF algorithm is demonstrated with ten bus generator systems, and the numerical results are compared and discussed with available algorithms. The numerical results indicate that the proposed algorithm is able to provide better solution with reasonable computational time.