Multichannel adaptive information systems can deliver services over different types of networks and access devices. Since different providers may offer either functionally equivalent or similar services, the quality of service (QoS) is a fundamental element of the service selection and the subsequent negotiation. This paper presents a taxonomy for quality dimensions, its application to different models of a multichannel information systems, and outlines requirements for a language to describe quality elements in a multichannel environment as modeled in the MAIS (Multichannel Adaptive Information System) Project.