Public procurement is being increasingly used to trigger innovations and thereby to enhance the effectiveness of the public sector. However, municipalities consider innovation procurement processes challenging. Also modularity is said to promote the innovations as it influences coordination processes and communication in supply chains. The aim of this study was to analyze how modular structures effect on innovations gained through public procurement in health and social services. We applied-cross case study and interviewed public authorities from three municipalities. We argue that characteristics of modularity are rather similar to mechanisms which, according to the literature, enhances innovations. Our data suggest that the organizations that used these mechanisms also received innovations in public procurement. However, also on this study innovation procurement processes turned out to be challenging. Some of these challenges were alleviated by using service vouchers. Service vouchers, both in the practice and the ideology, are rather modular in nature.  By using vouchers, providers’ innovation process can be supported and some of the problems related to public innovation procurement can potentially be avoided.