The present invention provides a method of imaging a subject's lung which comprises contacting the subject's lung with a matrix metalloproteinase inhibitor labeled with a radioisotope under conditions such that the inhibitor binds to matrix metalloproteinase in the lung, and then imaging the radiolabeled inhibitor bound to matrix metalloproteinase in the subject's lung.The invention also provides Ro 32-3555 labeled with a radioisotope.