Recent empirical studies have suggested that the implementation of a comprehensive peace agreement is the primary predictor of whether or not peace will last after a civil war. However, it is less certain what factors that lead to high implementation rates of peace agreements. Qualitative research has suggested that state capacity is a necessary condition for peace agreement implementation. Quantitively the relationship between state capacity and peace agreement implementation has only been controlled for in two studies. In this paper it is argued that this relationship has not been studied in a sufficient manner in either of them. Consequently, this study measures the relationship between state capacity and peace agreement implementation rate, operationalizing state capacity as the extraction rate and political reach of the state. This relationship is tested on 34 comprehensive peace agreements during the years of 1989 to 2015. However, the hypothesis did not find support as extraction rate has a negative correlation while political reach has a positive correlation. These findings are significant as they further the study on peace agreement implementation rate; how best to measure state capacity and moreover these findings can become important for what policies to prioritize in order to increase the implementation rate concerning peace agreements.