The cavitation phenomenon inside micro- and minichannel configurations was numerically investigated. The simulations for each channel were performed at different upstream pressures varying from 1 to 15 MPa. Two microchannel configurations with inner diameters of 152 and 254 mu m and two minichannel configurations with inner diameters of 504 and 762 mu m were simulated. To validate the numerical approach, micro-jet impingement from a microchannel with an inner diameter of 152 mu m was first simulated at different Reynolds numbers. Then, the mixture model was used to model the multiphase flow inside the channels. The results of this study present major differences in the cavitating flows between the micro- and miniscale channels and show that the pressure profile and vapor phase distribution exhibit different features. The static pressure drops to negative values (tensile stress) in microchannels, while the minimum static pressure in minichannels is found to be equal to vapor saturation pressure, and higher velocity magnitudes especially at the outlet are visible in the microchannels. It is shown that for higher upstream pressures, the cavitating flow extends over the length of the micro/minichannel, thereby increasing the possibility of collapse at the outlet. The effect of energy associated with turbulence was investigated at high Reynolds numbers for both micro/minichannels and its impact was analyzed using wall shear stress, turbulence kinetic energy and mean velocity at various locations of the micro/minichannels.