Objective: To determine the relative performance of T1rho and T2 relaxation times in disc degeneration assessment. Methods: Lumbar sagittal MRI was performed at 3 T in 52 subjects. With a spin-lock frequency of 500Hz, T1rho was measured using a rotary echo spin-lock pulse embedded in a three-dimensional (3D) balanced fast field echo sequence. A multi-echo TSE sequence was used for T2 mapping. Regions of interest (ROIs) were drawn over the T1rho and T2 maps, including nucleus pulposus (NP) and annulus fibrosus (AF). Eight- and five-level disc degeneration semi-quantitative grading was performed. Results: For NP, T1rho and T2 decreased quadratically with disc degeneration grades and had no significant trend difference (P = 0.40). For AF, T1rho decreased linearly as the disc degenerated and had a slope of -3.02 and -4.56 for eight- and five-level gradings respectively; while the slopes for T2 values were -1.43 and -1.84 respectively, being significantly flatter than those of T1rho (P < 0.001). There was no significant difference in T1rho and T2 values for both NP and AF among discs of grade 5/8 to 8/8 degeneration. Conclusion: T1rho is better suited for evaluating AF in degenerated disc than T2. In NP, T1rho and T2 decrease in a similar pattern following disc degeneration. Key Points: • MRI provides unique information about the lumbar disc nucleus pulposus • Both T1rho and T2 relaxation times decrease similarly following disc degeneration • AF T1rho relaxation times decrease progressively faster than T2 relaxation times • T2 and T1rho relaxation times do not reduce further by disc-space narrowing © 2012 European Society of Radiology.