Congenital diaphragmatic hernia (CDH) is associated with a high mortality rate (over 50%). Prediction is more or less correlated to lung volume at 26 weeks, currently based on lung-to-head ratio (LHR) (Metkus, J Ped Surg 1996; 31: 148–152). Alternatively, lung volume measurement is performed by magnetic resonance imaging (MRI). (Mahieu-Caputo BJOG 2001; 108: 863–868). We conducted an experimental study to determine agreement and precision of MRI fetal organs volume determination versus volume determination at macroscopy (necropsy). In a total of 9 sheeps under general anaesthesia, 14 fetal lambs underwent MRI. Lungs where measured in T2 weighted images in several planes (axial, coronal and sagittal), livers and kidneys where measured in one plane. Lungs where divided in hypoplastic lungs (DH was created at a mean gestational age (GA) of 73 days, n = 10), and normal lungs (n = 18). Necropsy was done less then 24 hours after MRI (at a mean GA of 120 days). At necropsy, organ volumes where determined by the volume displacement method. Ranges volume at necropsy, means ± SD, bias (mean of the difference necropsy volume-MRI volume) and precision (SD of the difference), are represented. Analysis is made according to Bland and Altman (The Lancet 1986; i: 307–310). There was a better agreement in small volumes (Kidney, bias = 2.01) comparing to bigger volumes (Liver, bias = − 35.49) and when lung volumes where measured in the axial plane (bias = − 15.58) comparing to coronal (bias = − 20.22) or sagittal planes (bias = − 26.62). Normal lung volumes in axial planes showed a better agreement comparing to CDH lungs, but this was not the case in the coronal or the sagittal planes. Bland and Altman analyses showed no clinically important systematic errors in the MRI measurements. MRI performed in the axial plane is reliable in predicting CDH as well as normal lung volumes in fetal lamb.