The dehumidifier and regenerator are key components in liquid desiccant air conditioning systems. Many researchers have developed mathematical models of the coupled heat and mass transfer processes in the dehumidifier or regenerator, and most of the models were solved numerically. Compared with numerical solutions, analytical solutions have more advantages in analyzing the parameters that affect the heat and mass transfer performance. This paper presents analytical solutions of the air and desiccant parameters inside the parallel flow, counter flow and cross flow dehumidifier/regenerator under some reasonable assumptions based on the available heat and mass transfer models. The analytical solutions of the air and desiccant parameters within the dehumidifier/regenerator show good agreement with the corresponding numerical results, and the analytical solutions of the enthalpy and moisture efficiencies agree well with experimental findings. The method developed here can be used in the optimal design of the dehumidifier or regenerator. (C) 2007 Elsevier Ltd. All rights reserved.