The purpose of this study was to correlate the CT and pathologic findings after radiofrequency ablation (RFA) of rabbit lung and evaluate the therapeutically effective area. RFA was performed in eight rabbit lungs, and ablated regions were imaged immediately after RFA (n=8) and 1 week later (n=4). Immediately after RFA, the ablated regions showed ground-glass opacity. At one week, the ablated region showed very dense opacity, which corresponded to necrotic tissue. Ground-glass opacity signified the therapeutically effective area that would later turn into necrosis.