Objective To investigate the signal intensity and apparent diffusion coefficient （ADC） of bone marrow of normal adult man on diffusion weighted imaging （DWI）. Methods Fifteen healthy volunteers and thirty-eight patients with benign prostatic hyperplasia or normal prostate were enrolled in this study

with age range 28-82 years old （mean 55.26 ± 18.05 years）. All people were examined with large field DWI on a 3.0T magnetic resonance scanner

which ranges from the top of head to the lower limb. The signal-to-noise ratio （SNR） on the DWI and ADC of lumber vertebra at renal hilum level

left ilium and superior segment of left femur were measured. The measured SNR and ADC value of the above sites were compared by one way analysis of variance and their correlations with age were investigated by Pearson’s correlation analysis. Results The SNR of lumber vertebra

left ilium and left femur showed no significant difference （F = 0.271

P = 0.763）. The SNR of lumber vertebra （r = 0.309

P = 0.024） and left ilium （r = 0.359

P = 0.008） showed positive correlation with age

while the SNR of left femur showed no correlation with age （r = -0.163

P = 0.283）. The ADC of lumber vertebra [（0.617 ± 0.177） ×10-3 mm2/s] was significantly higher than that of left ilium [（0.404 ± 0.112） ×10-3 mm2/s

P < 0.001] and left femur [（0.362 ± 0.092） ×10-3 mm2/s

P < 0.001]

while the ADC of left ilium and left femur had no significant difference. The ADC of lumber vertebra

left ilium and left femur showed no correlation with age. Conclusion Understanding of age-related changes of normal adult bone marrow on DWI is very important to differentiate the normal bone marrow and abnormal lesions.