The reference method for the determination of urinary protein excretion in patients with kidney diseases is the measurement of 24-h protein excretion. But 24-h. urine collection is unreliable and cumbersome. So protein/creatinine ratio (P/C) in spot urine is used to determine proteinuria. In this study we investigated if P/C ratio in spot urine is reliable to determine proteinuria. This study included 60 subjects hospitalized in Izmir Ataturk Education Hospital Nephrology Clinic with different type of kidney diseases. P/C ratios in spot urines and protein excretion in 24 h. urine specimens were calculated. Measurement of 24 h. urine prot ein is considered as a reference method. We compared the two methods. There was a strong positive correlation between the results of the two methods (p<0.05, r=0.92) Area under the ROC curve was 0.946 when we evaluate P/C ratios. The best P/C cut-off values to detect abnormal or nephrotic proteinuria were, respectively, 0.15, 0.35 and 0.56.Our findings supported the use of spot urine P/C ratio to determine proteinuria in patients with kidney diseases.