Abstract—Selecting requirements for a release of software is a difficult undertaking as people have trouble comparing requirements of different types and have natural biases towards short-terms gains over longer-term sustainability. Portfolio theory is proposed as a solution to this problem, as it provides a method for balancing investment options to maximize the likelihood of a given return. This approach is explored generally and through an example. The results suggest portfolio theory can be applied for this purpose. Applying portfolio theory to determine the amount of development time that should be spent on different types of requirements shows the most potential, especially when data on expected risks and returns is limited.