This paper compares the dichromate method with the photoelectrochemical method (PeCOD), with regards to the influence of chloride and turbidity with chemical oxygen demand (COD) determination. Whereas the upper limits of chloride concentration are well established for both techniques, the influence of turbidity and the combined interference of underdosing chlorides and turbidity together have never been reported. When only potassium hydrogen phthalate or sorbitol were analyzed, the results show no significant difference in either method when 607 mg Cl -L -1 or 230 NTU of turbidity were added to the samples within the range of 100-900 mg L -1 COD. However, a combined effect of these two interferents leads to significantly different results, mainly for low COD range, as evidenced by the Student's t-test for paired samples (p = 0.05).