Teleradiology is probably the most successful eHealth service available today. Its business model is based on the remote transmission of radiological images (e.g. X-ray and CT-images) over electronic networks, and on the interpretation of the transmitted images for diagnostic purpose. Two basic service models are commonly used teleradiology today. The most common approach is based on the message paradigm (off-line model), but more developed teleradiology systems are based on the interactive use of PACS/RIS systems. Modern teleradiology is also more and more cross-organisational or even cross-border service between service providers having different jurisdictions and security policies. This paper defines the requirements needed to make different teleradiology models trusted. Those requirements include a common security policy that covers all partners and entities, common security and privacy protection principles and requirements, controlled contracts between partners, and the use of security controls and tools that supporting the common security policy. The security and privacy protection of any teleradiology system must be planned in advance, and the necessary security and privacy enhancing tools should be selected (e.g. strong authentication, data encryption, non-repudiation services and audit-logs) based on the risk analysis and requirements set by the legislation. In any case the teleradiology system should fulfil ethical and regulatory requirements. Certification of the whole teleradiology service system including security and privacy is also proposed. In the future, teleradiology services will be an integrated part of pervasive eHealth. Security requirements for this environment including dynamic and context aware security services are also discussed in this paper. Copyright (c) 2009 Elsevier Ireland Ltd. All rights reserved.