Design phase is one of the phases that can largely affects the lowering of performance level, i.e. conflicts in design documents, numerous modifications to be performed and the difficulty that causeatlate stages of the design process, and consequently delay in delivery and sometimes fail to reach the project objectives. Building Information Modeling (BIM) system is one of the effective methodologies that offers many privileges that could take part in solving these problems. The purpose of this study is revealing the influence of implementing BIM in design phase, by comparing it with traditional CAD-based systems. Case studies have been conducted for projects of residential buildings during design phase in architectural part. Findings indicate that implementing BIM in design phase for architectural discipline have shortened the time needed for producing design documents by 75%. This study could be utilized by any company working in the architectural design field, and encourages decision makers to start using BIM. Furthermore there still is a need foran extensive studies to imply other kinds of buildings and more disciplines of AEC industry.