Carbon-13 nuclear magnetic resonance spin-lattice relaxation times and nuclear Overhauser enhancements were measured as functions of temperature for the hydrogen-bearing carbons in 9-fluorenone, 4-methyl-9-fluorenone, and 4,5-dimethyl-9-fluorenone. Reorientational diffusion constants were obtained from the dipolar T1 values. Isotropic overall molecular motion was assumed, and the methyl group rotation was separated from the overall molecular reorientation by the method of Woessner. Arrhenius plots of the dependence of the rotation rates on temperature provided values of the energy barriers for molecular reorientation and methyl group rotation.