The reaction rate constant for the cyano (CN) radical with hydrogen and deuterium has been determined over the temperature range 293-380 K. The CN radical was detected by time-resolved near-infrared absorption using the CN red system (A2 Pi <-- X(2)Sigma) (2,0) band near 790 nm. These measurements were carried out at low pressures of Ar or He as carrier gas. The diffusion rate of CN in these mixtures was inferred from the diffusion rate of HCN(000) determined using time-resolved infrared absorption of HCN(000) around 3.0 mu m, simultaneously with the detection of CN. These measurements provide accurate thermal rate constant data that will enable a detailed comparison to be made between theoretical predictions and experimental measurements for this prototypical reaction system.