Purpose: To evaluate the feasibility of in-vivo 1H magnetic resonance spectroscopy (1H-MRS) for differentiation between hepatic and renal cysts, with emphasis on the analysis of cystic content. Materials and Methods: The 1H-MR spectra of 43 cystic lesions (15 hepatic and 28 renal) obtained using in -vivo 1H-MRS at 1.5 T and with a localized proton STEAM sequence were evaluated. We calculated the ratio of the peak area of lipid/water ($R_{lipid/water}$), protein/water ($R_{protein/water}$) and lipid/protein ($R_{lipid/protein}$), paying particular attention to identifying differences in peak area ratios between the two types of cyst. Results: The 1H-MR spectra from 26.7% (4/15) of hepatic and 67.9% (19/28) of renal cysts showed the lipid peak as most prominent. Mean${pm}$standard deviations of the $R_{lipid/water}$ of hepatic and renal cysts were 0.38${pm}$0.30x10-6 and 8.42${pm}$23.24x10-6, respectively; for $R_{protein/water}$ the corresponding figures were 0.83${pm}$0.74x10-6 and 1.50${pm}$2.94x10-6, and for $R_{lipid/protein}$, 0.57${pm}$0.64 and 2.44${pm}$3.26. All differences were statistically significant (p<0.05), and positive correlation between lipid and protein in hepatic and renal cysts was demonstrated. Conclusion: The different in-vivo 1H-MRS findings, for hepatic and renal cysts can be used in comparative study of cystic tumors of the liver and kidney.