Cloud computing is an emerging paradigm with three basic service models such as Software as a Service (SaaS), Platform as a Service (PaaS), and Infrastructure as a Service (IaaS). This paper focuses on different kinds of PaaS frameworks. PaaS model provides choice of cloud, developer framework and application service. In this paper, detailed study of four open PaaS frameworks like AppScale, Cloud Foundry, Cloudify, and OpenShift are explained with the architectural components. We also explained more PaaS packages like Stratos, mOSAIC, BlueMix, Heroku, Amazon Elastic Beanstalk, Microsoft Azure, Google App Engine and Stakato briefly. In this paper we present the comparative study of PaaS frameworks.