The focus of the paper is on the effect of design parameters on environmental performance of the urban patio. This paper presents the results of a case study of different courtyards in Lisbon. Short-term monitoring was undertaken to assess the effects of design parameters, such as geometry, orientation and finishings on environmental performance of four different patios. Air temperature was recorded for eight days during August 1996 and spot measurements of air velocity were taken. The results are compared and discussed. The paper also examines the results of solar radiation studies carried out to assess possible improvements in courtyard thermal performance.