Objective: To investigate the enhancement basis and the mechanisms of solitary pulmonary nodules (SPNs) by comparing the differences in microvascular structure between benign and malignant lesions. Methods: Dynamic contrast-enhanced CT scan was performed on 53 patients with SPNs (diameter<3 cm. 38 peripheral lung cancers, 5 hamartomas, 10 inflammatory lesions) using a Siemens Plus S or a Marconi MX8000 multi-slices spiral CT scanner. The time-attenuation curves were interpreted. The microvascular density (MVD) and the continuity of the microvessels’ basemental membrane in the dissected specimens were observed with the ABC (avidin-biotin-complex) immuno-histochemical method in all patients. ResultS:The CT enhancement values of lung cancer (49. 05±16. 08 HU) and inflammatory lesions (49. 59±21. 30 HU) were significantly higher than those of hamartoma (8. 98±4. 56 HU) (t = 7. 48. P<0. 05; t = 8. 35, P<0. 05). But the enhancement of lung cancer was similar to that of inflammatory lesions (t = 0. 76. P>0. 05). The time-attenuation curve of inflammatory lesions tended to increase faster and reached a higher peak compared to the lung cancer, and both of them maintained a high plateau after crossing. The hamartoma showed a slight increase in the time-attenuation curve and demonstrated a low-plateau curve. The MVD of SPNs was positively correlated with CT enhancement (r=0. 8051). The microvascular counts of peripheral lung cancer (48. 45±10. 09) and inflammatory lesions (19. 60±19. 94) were significantly higher than those of hamartoma (8.70±7.30) (t = 11.64, P<0.001;t = 6. 09. P< 0. 001). but no significant difference was found between lung cancer and inflammatory lesions (t= -0. 26, P = (). 799). There was no difference in the continuity of basement membrane between nodules with an enhancement less than 30 HU and those with an enhancement higher than 30HU (x2 = 3. 13, P>0. 05 ). Conclusion: The microvascular counts mainly contribute to the enhancement value of SPNs. The basement membrane is not related to nodule enhancement, but it might influence the pattern of the time-attenuation curve. Objective: To investigate the enhancement basis and the mechanisms of solitary pulmonary nodules (SPNs) by comparing the differences in microvascular structure between benign and malignant lesions. Methods: Dynamic contrast-enhanced CT scan was performed on 53 patients with SPNs (diameter <3 cm The time-attenuation curves were interpreted. The microvascular density (MVD) and the continuity of the microvessels’. 38 peripheral lung cancers, 5 hamartomas, 10 inflammatory lesions) using a Siemens Plus S or a Marconi MX8000 multi- basemental membrane in the dissected specimens were observed with the ABC (avidin-biotin-complex) immuno-histochemical method in all patients. ResultS: The CT enhancement values ​​of lung cancer (49.05 ± 16.08 HU) and inflammatory lesions . 59 ± 21. 30 HU) were significantly higher than those of hamartoma (8. 98 ± 4. 56 HU) (t = 7. 48. P <0.05; t = 8. 35, P <0.05) But the enhancement of lung cancer was similar to that of inflammatory lesion s (t = 0.76, P> 0.05). The time-attenuation curve of inflammatory lesions tended to increase faster and reached a higher peak compared to the lung cancer, and both of them maintained a high plateau after crossing. The The MVD of SPNs was positively correlated with CT enhancement (r = 0. 8051). The microvascular counts of peripheral lung cancer (48. 45 ± 10 . 09) and inflammatory lesions (19. 60 ± 19. 94) were significantly higher than those of hamartoma (8.70 ± 7.30) (t = 11.64, P <0.001; no significant difference was found between lung cancer and inflammatory lesions (t = -0.26, P = (). 799). There was no difference in the continuity of basement membrane between nodules with an enhancement less than 30 HU and those with an enhancement higher than 30HU (x2 = 3.13, P> 0.05). Conclusion: The microvascular counts mainly contribute to the enhancement value of SPNs. T he basement membrane is not related to nodule enhancement, but it it might influence the pattern of the time-attenuation curve.