Software process improvement is a popular way to increase the quality of software and the predictability of software engineering. In order to acquire effective processes, the software process improvement needs to be continuous. In this article we analyze the improvement models, which aim to introduce detailed actions for continuous process improvement and the key success factors of improvement based on various literary sources. As a result of the comparison of the two, we have pointed out issues, which, if considered in the improvement models, would help organizations in their improvement efforts.