The diffusion coefficients of N2O in aqueous piperazine (PZ) solutions have been determined using the Taylor dispersion technique over a temperature range from (293 to 333) K and a concentration range from (0.3 to 1.4) mol·dm−3 PZ. The experimental results have been compared to literature values. Diffusion coefficients of N2O in aqueous PZ solutions can be estimated by using a modified Stokes−Einstein relation with sufficient accuracy for engineering purposes. The diffusion coefficient of CO2 in an aqueous PZ solution can be estimated by means of the “N2O analogy”. The use of the Taylor dispersion technique for determination of gas diffusivities in liquids is given in detail.