AIM: To investigate the effects of diode laser treatment on ocular biometric parameters in premature infants with retinopathy of prematurity (ROP). METHODS: Premature infants who received diode laser treatment for ROP (n=68) and premature infants with spontaneous regressed ROP without treatment (n=50) were performed longitudinal ocular biometric measurements including anterior chamber depth, lens thickness and axial length as follows: 1d prior to laser treatment, and 3, 6, 9, and 12mo after the laser treatment. RESULTS: The mean birth weight, gestational age and initial examination time values were 936.53±302.07 g, 26.66±2.42wk, 36.26±2.73wk in the treatment group and 959.78±260.08 g, 27.28±2.10wk, 36.56±2.54wk in the control group. There was no statistically significant difference in these demographic characteristics of the groups. Anterior chamber depth, lens thickness and axial length demonstrated statistically significant linear increases during the study period in the two groups (P<0.001 for each). There were no statistically significant differences between the two groups in terms of anterior chamber depth after laser treatment. Measurements of the lens thickness at 9th and 12th months (9th month 3.70±0.22 vs 3.60±0.21 mm, P=0.017; 12th month 3.81±0.21 vs 3.69±0.22 mm, P=0.002) and the axial length at 12th month (19.35±0.79 vs 19.13±0.54 mm, P=0.031) after laser treatment were statistically higher in the treatment group. CONCLUSION: Diode laser retinal photocoagulation treatment in premature infants seems to increase the lens thickness and axial length.