Previous studies have noted the morphologic changes of lumbar disc herniation (LDH) in conservative treatment and predictive value of the resorption of LDH by using contrast-enhanced MRI. However, there are few reports that note the predictive value of plain, non-enhanced MRI. Therefore, no definite predictive factors for the resorption of LDH have been detected on plain MRI. Thirty-four patients with lower limb pain receiving conservative treatment were followed for more than 6 months. MRI was performed every 3 months. The findings of the first MRI in the patients who finally had resorption of LDH (R-group, 21 patients) were compared with those of the patients who exhibited no resorption of LDH (N-group, 13 patients). The MRI evaluation included the signal intensity of LDH, migration of LDH. The transition of the visual analogue scale (VAS) of lower limb pain was also compared. The R-group had significantly more patients with iso-signal intensity in comparison to the signal intensity of the nucleus pulposus observed on T1 weighted images (WI) and high-signal intensity in comparison to the signal intensity of the annulus fibrosus observed on T2 WI, whereas the N-group had more patients with the high-signal intensity on both T1 and T2 WI. The R-group had significantly more patients with migration. The VAS significantly improved at 3 and 6 months in both groups. However, no statistically significant difference was detected between the 2 groups. It is very valuable that the results clearly indicate the predictive factors on plain MRI concerning the resorption of LDH. The study also showed that lower limb pain would gradually improve even in the patients who exhibited no resorption. Therefore, it is important in the treatment of LDH to observe the clinical symptoms carefully without overestimating MRI findings.