Humidification dehumidification desalination process is viewed as a promising technique for small capacity production plants. The process has several attractive features, which includes operation at low temperature, ability to combine with sustainable energy sources, i.e., solar, geothermal, and requirements of low level of technical features. This paper evaluates the characteristics for several layouts for the humidification dehumidification desalination process. The common feature among these processes is the air humidification tower, where the humidity of the ambient air is increased to saturation at the desired design temperature. The main difference among various layouts is the dehumidification process. The most common scheme is to use a condenser to reduce the humidified air temperature and to condense the fresh water product. Other possible layouts includes vapor compression, desiccant air drying, and membrane air drying. The design equations are developed for the humidification/condenser and the humidification/desiccant systems. Discussion and performance evaluation of various layout shows the need to fully optimize these configurations. This is necessary to obtain the best design and operating conditions that give the minimum product cost.