Background Diffusion-weighted imaging plays a key role in the imaging of acute pyelonephritis by MRI. However the use of respiratory triggering is challenging and time-consuming in children. Diffusion tensor imaging without respiratory triggering might provide satisfying images of the moving kidneys. Objective To compare mean diffusivity diffusion tensor images obtained with free breathing with diffusion-weighted images obtained with respiratory triggering. Materials and methods Thirty-one children with suspected acute pyelonephritis underwent axial diffusion tensor imaging acquisition with free breathing and axial and coronal diffusion-weighted imaging acquisitions with respiratory triggering. We compared image quality and detection of nephritis between the two sequences. Results Diffusion tensor imaging demonstrated agreement with diffusion-weighted imaging in all cases, with no difference in the detection of nephritis areas. The image quality was significantly better with diffusion tensor imaging (P<0.01). Conclusion Diffusion tensor imaging could replace diffusion-weighted imaging for diagnosis of acute pyelonephritis.