This paper intends to discuss the combined economic emission hydrothermal scheduling [Energy Convers. Manage. 51 (2010) 561-571], while an improved Quantum-behaved Particle Swarm Optimization (QPSO) method has been utilized to solve the proposed optimization problem. The economic/environmental hydrothermal scheduling problem is a non-convex optimization problem, which is subjected to several equality and inequality constraints. These constraints relate to the power balance and the technical limitations of thermal and cascaded hydro units. The solutions obtained in the original paper [1], do not satisfy the constraint on the power produced by hydro generating units that should be positive at any time of the scheduling period. In this regard, this paper indicates this inaccuracy occurred in the original paper [1], and solves the problem using epsilon-constraints technique and lexicographic optimization to present the solutions satisfying all the constraints of the mentioned problem. (C) 2015 Elsevier Ltd. All rights reserved.