Slow gas diffusion limits mass transfer and is detrimental in various device applications, such as fuel cells, batteries, membrane engineering, and catalysis. In fuel cells, the gas diffusion coefficient, called the diffusivity, correlates with the concentration polarization (CP) energy loss and such important parameters associated with electrode materials as porosity and tortuosity. Although three dimensional (3D) diffusion and 3D diffusivity have been investigated via theoretical computing and modeling, a technique allowing for the direct measurement of 3D diffusivity in fuel cells is still lacking. In this report, an electrochemical cell is proposed for the measurement of 3D diffusivity in fuel cells. This device enables one to measure simultaneously diffusivity in three electrode directions. A 3D diffusivity measurement leads directly to a precise evaluation of the 3D concentration polarization, the 3D limiting current density (LCD), the 3D electrode porosity and the 3D electrode tortuosity. Based on the diffusivity measurement in three electrode directions, a rational selection of the optimum electrode operation direction can be realized.