Quality is one of the central concepts in urban design knowledge and profession - naturally with a great theoretical and practical significance. Apart from theoretical importance, due to quality crisis currently experienced in most Iranian urban environments, quality has become a serious question from a practical point of view.
Many officials, academicians, and practicing urban designers have increasingly expressed their concerns over lack of quality in urban design of the country. However, due to equivocal and elusive nature of the concept of Quality, so far there seems little consensus among the diverse views. To provide a common understanding of urban design quality, it seems as if some theoretical clarification of the concept is needed. This paper aims at inquiring the concept of urban design quality, by developing a theoretical framework to explain the concept, identifying its components. The paper consists of five major parts. First, the concept of Quality is etymologically discussed. Next, the concept is examined in terms of "modes of existence". Then, a review of the literature on the notion of "good" urban design and the qualities concerned is presented and the criteria applied in a number of urban design checklists is examined and the results are reported. Finally, the paper concludes that:
1- Urban design quality could be effectively explained by means of an enhanced version of Canter's (1977) pioneering "place" paradigm as suggested by this study and entitled "Sustainable Place Model";
2- Urban design quality comprises three components namely "experiential-aesthetic quality", "functional quality", and "environmental quality".