An appreciation of functional and morphological characteristics is fundamen
tal to the understanding of diffuse lung disease. The detailed information
available from high-resolution computed tomography (HRCT) and the facility
to subjectively or objectively quantify disease has elucidated the sometime
s complex pulmonary function profiles of several diffuse lung diseases. The
many reasons why correlations between the extent of HRCT abnormalities and
physiological measures of disease may be less strong than expected and are
considered in this review.