<i>Background:</i> N-terminal pro-B-type natriuretic peptide (NT-proBNP) plasma levels are associated with congestive heart failure severity, and are an important diagnostic tool for assessing patients with acute dyspnea. Reduced renal function increases NT-proBNP concentrations, and therefore it might be a confounding factor in chronic kidney disease (CKD) patients. <i>Objective:</i> The aim of the present study was to relate NT-proBNP plasma levels to different stages of renal function assessed with different methods in older adult subjects admitted because of dyspnea. <i>Methods:</i> NT-proBNP plasma levels (Roche Diagnostic, Mannheim, Germany) were measured in 134 older adult patients (age: 80 ± 6 years) admitted to hospital because of dyspnea. Anthropometrics, anamnesis, and biochemical data were collected. Glomerular filtration rate (GFR) was evaluated with different equations, the 4 variables MDRD equations (GFR_MDRD186, GFR_MDRD175), Mayo Clinic Quadratic formula (GFR_MAYO), and the new CKD-EPI formula (GFR_CKD-EPI). Patients were classified into the five K/DOQI stages of CKD and median NT-proBNP values were calculated evaluating their relationship with GFR. <i>Results:</i> Median NT-proBNP values were better stratified into the five K/DOQI stages by GFR_MAYO (stage 1 (n = 10) 1,640 pg/ml vs. stage 2 (n = 61) 2,371 pg/ml vs. stage 3 (n = 42) 3,815 pg/ml vs. stage 4 (n = 18) 6,320 pg/ml vs. stage 5 (n = 3) 7,256 pg/ml, p = 0.017). However, similar results were obtained with the other formulae. NT-proBNP was negatively correlated with GFR as evaluated with all the different formulae (r –0.25 to –0.29; all p < 0.01). Multiple regression analysis confirmed the independent association between LnNT-proBNP and GFR. <i>Conclusion:</i> NT-proBNP plasma levels progressively increase with worsening of renal function, and appear to be related to the five K/DOQI stages of CKD. For this purpose, GFR assessed with the GFR_MAYO formula appears to better stratify NT-proBNP in older adult subjects. Renal function should be considered when interpreting NT-proBNP levels in older adult patients admitted for dyspnoea.