The purpose of this study is to find the characteristics of space utilization and the problems that follows after converting in a new developmental residential area. This study used the content-analysis method and analysis was made on the floor plans for 95 different conversion cases. Above all, 190 unit plans (the unit plans for conversion before and after) were analyzed. The results of this study were as follows; 1) There were 8 types of conversion according to such usages as residential, commercial and residential-commercial buildings. 2) In the case of conversions, from residential to commercial, there was a tendency each floor was integrated to exclusive use for commercial or commercial with small portions of residential usage. And in the case of conversions from commercial to residential, there was a tendency that all space of each floor were changed to exclusive usages for residential purposes. 3) In case of usage conversion from commercial to residential, there were constraints for balcony installation, because of its original lot-structure and building equipments. Also, when the basement was converted for residential purpose, there was no possibility for an extra lighting or ways to ventilate the area.