Presented article describes the optimization process of the cross-flow Maisotsenko cycle indirect evaporative air cooler. The optimization was performed on the basis of three carefully selected individual quality criteria. The optimization was performed for five influence factors (inlet temperature and relative humidity, primary air mass flow rate, working to primary air ratio and relative length of the initial part). The optimization was performed with two methods: single-parameter and multi-parameter compromise method. The single parameter optimization lead to the unsatisfactory results, due to the different trends shown by the quality criteria under identical variation of input parameters. The multi-parameter optimization was based on analysis of the Harrington function of desirability. The results of optimization allowed establishing optimal range of operational and geometrical conditions for the presented exchanger and establishing the optimal climate conditions for its effective operation. (C) 2016 Elsevier Ltd. All rights reserved.