The lateral transport of dopants in silicon films on insulators during laser recrystallization is investigated. The dopants implanted locally in silicon films on insulators are found to be transported in the forward direction of the laser scan as well as the backward direction. Both transport lengths from the originally implanted region are measured as a function of the laser scan velocity. The transport mechanism is explained by taking into account a liquid phase diffusion and a segregation of impurities depending on the crystallization speed. The diffusion coefficients of (1.2±0.2)×10−4and (1.3±0.4)×10−4cm2/s for arsenic and boron, respectively, in molten silicon are obtained.