To achieve a sustainable residential area, open spaces must promote comfort and invite people to stay outdoors and prolonging their stays, which will contribute to a more lively residential areas offering greater interaction between its inhabitants. Thermal comfort is an essential factor that should be considered in any urban design process, urban design characteristics of any project have a strong influence on human thermal comfort at outdoor spaces, like its spatial organization and landscape elements, the paper aims to assess the impact of spatial organization differentiation on thermal comfort of inhabitants in two different residential multi-story complexes in Duhok city. Thermal comfort for an urban context in hot and semi-dry climate zone based on the physiologically equivalent temperature (PET) index have been adopted and simulated by ENVI-met program, two simulations were conducted for each complex through climatic data of the hottest day in summer and coldest day in winter of 2013. The results reveal that the two complexes have not provided a comfortable space during the two seasons in general, but it showed that the second complex has a better performance in this respect for the two seasons, in spite of the poor landscaping it has, the paper concludes the importance of the urban design characteristics represented by the spatial organization on thermal comfort of the inhabitants at open spaces at such kind of projects and climate, and the necessity of adopting more compact and close spaces.