In recent years, an increasing number of Chemical Engineering Software (CES), which play an important role in improving efficiency in the petroleum industry, has been introduced to the market. Generally, software is the product of intellectual creativity, but protection of the intellectual property residing in software is the subject of some controversy. This paper explores the legal protection of software products and its evolution over time. The approach of selected countries to software protection is reviewed in comparison with the Iranian legal regime in the same field. Important concepts that need to be considered in acquiring effective protection of CES are presented. Software-related patent classifications were reviewed and US inventions relating to them were collected using a professional patent data base. Finally, the CES inventions in each classification were investigated in comparison to the total number of software patents. Consequently, the most referable classification for CES invention has been determined in this paper.