© 2017 Sans et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Background/Aims: Height-adjusted total kidney volume (htTKV) is the best marker of disease progression in early autosomal dominant polycystic kidney disease (ADPKD) when renal function still remains normal. The usefulness of cystatin-C as a biomarker to assess renal function according to renal volume has not been studied in ADPKD patients. Methods: Observational and cross-sectional study of 62 ADPKD patients. htTKV, creatinine and cystatin-C estimated glomerular filtration rate (eGFR) were determined. Correlations between htTKV and eGFR were studied. A control group was used to determine the association between renal function differences and htTKV. Results: htTKV significantly correlated with cystatin-C-eGFR (r = -0.384, p = 0.002) but not with creatinine-eGFR (r = -0.225, p = 0.078). With htTKV stratified into tertiles, a significant difference of cystatin-C-eGFR but not in creatinine-eGFR was detected in the third tertile when compared with the first tertile group (110.0±22.2 vs 121.3±7.2; p = 0.023 and 101.8±17.2 vs 106.9±15.1; p = 0.327 respectively). When cystatin-C-eGFR of the controls was used as the reference, htTKV above 605 ml/m identified with a 75% sensitivity and 84.9% specificity those patients with a significant worse kidney function. However, this cut-off value could not be identified using creatinine-eGFR. Conclusions: Cystatin-C-eGFR but not creatinine-eGFR correlated with htTKV in ADPKD patients in early stages of the disease. Differences in cystatin-C-eGFR but not in creatinine-eGFR have been identified through htTKV tertiles. A htTKV above 605 ml/m is associated with a worse renal function only if cystatin-C-eGFR is used. Cystatin-C-eGFR should be studied in prospective studies of early stages of ADPKD to determine its usefulness as an early marker of disease progression.