Radiology by its nature is intricately connected to the Internet and is at the forefront of technology in medicine. The past few years have seen a dramatic rise in Internet-based technology in healthcare, with imaging as a core application. Numerous Internet-based applications and technologies have made advancements of wide steps into medicine, and for radiology it is more effective than in other clinical specialties. Picture archiving and communication system (PACS) is a computerized means of replacing the roles of conventional radiological film: images are acquired, stored, transmitted, and displayed digitally. When such a system is installed throughout the hospital, a filmless clinical environment results. Teleradiology has made using the Internet explorer possible to access to images and patient findings, to browse, view and write radiological reports on any computer in any location. Teleradiology can provide services in rural areas where there is no a specialized radiologist at any time. As well, in developing countries or where there is radiologists shortage in any country. PACS underwent a rapid development for the past 15 years, influenced by new technologies, faster network connections and other technical improvements, aimed to replace former film based medical images. This article aims to clarify the terms, roles, importances & Implementations of PACS & teleradiology.