AIM: To analyze the correlation between macular morphology and function in eyes with diabetic macular edema (DME). METHODS: Fifty-five eyes with different visual acuity (VA) of 32 patients who suffered from DME were analyzed using multifocal electroretinography (mfERG) and optical coherence tomography (OCT). The parameters of mfERG including implicit times and response amplitude were compared to those of 50 normal eyes of 36 age-matched subjects. Correlation analysis was performed between VA, the parameters of mfERG including implicit times and response amplitude, and the central macular thickness (CMT). RESULTS: The amplitude of N1 and P1 were significantly decreased and their latency were significantly increased in five ring regions of the retina in patients with DME. There was statistically significant correlation between logMAR BCVA and P1 amplitude densities in rings 1-4 (r=-0.306, -0.536, -0.470, -0.362; P=0.023, <0.01, <0.01, 0.007 respectively), N1 amplitude in ring 2 and ring 3 (r=-0.035, -0.286; P=0.019, 0.034 respectively). There was poor correlation between the CMT and best-corrected visual acuity (BCVA; r=0.288, P=0.033), but there was no significant correlation between CMT and amplitude or implicit time of N1 and P1 (P>0.05) in the central macular ring. Multiple stepwise regression analysis showed that P1 amplitude density in ring 2 was the only contributor to the VA. CONCLUSION: It seems to be more appropriate of combining use of mfERG with OCT for the evaluation of macular function in eyes with DME.