Objective: The aim of this study was to determine an optimal slice thickness that was efficient in revealing lobula-tion of malignant solitary pulmonary nodules (SPNs) on multi-slice spiral computed tomography (MSCT) images preliminarily. Methods: Fifty patients with malignant SPNs (diameter ≤ 3 cm) underwent multidetector-row computed tomography of the chest in a single-breath-hold technique. The raw data were acquired with a collimation of 0.625 mm. Three sets of contiguous images were reconstructed with 1-, 2-, and 5-mm slice thickness, respectively. The lobulation sign of SPNs on the computed tomography (CT) images presented in 1-, 2-, and 5-mm slice thickness was compared. Using the 1-mm sections as the gold standard, an optimal slice thickness in revealing lobulation sign of SPNs was determined. Results: The 1-mm-thick images CT revealed 98 lobulations (25 with chord distance 2 mm) of 45 malignant SPNs. 18 lobulations with chord distance 0.05). 36 lobulations with chord significant difference in lobulations number between that revealed in 5-mm-thick images and that in 1-mm-thick images (P = 0.264 > 0.05). Conclusion: It is suggested that the use of 1-mm slice thickness is suitable in revealing lobulations with chord distance 2 mm.