In this paper, flashover process between conductive paths (CPs) on a circuit board under very fast impulse voltages is investigated. For this purpose, an electronic circuit board of FR4 with CPs ( electrodes), which are seven different geometrical shapes on it, is prepared. Flashover experiments are performed by applying very fast impulse voltages having 50-ns front duration between each two CPs on the circuit board. The flashovers between these paths are observed for the different geometries of the CPs. The experimental study is supported with electric field calculations. Finite-element method is used to analyze potential and electric field distribution between the CPs. The CPs with respect to their geometries are evaluated point-of-view reliability of circuit boards.