Cavitation is one of the main sources of flow instabilities arising during the operation of hydraulic equipment and is also a cause of erosion wear of its operating elements. In this regard, the elaboration and development of various methods of cavitating flow control is an urgent problem for hampering cavitation evolution and reducing its negative impact. One of these methods is modification of the surface of a hydrofoil. In the paper, the results of an experimental study of a cavitating flow around a grooved 2D hydrofoil are presented in comparison with the ones for the original profile. In order to analyze the spatial structure and time dynamics of partial cavities and evaluate their integral parameters, a high-speed imaging was applied. The flow velocity over the hydrofoils and behind them was measured by a PIV technique. On the modified section, cavitation initiates in form of individual bubbles travelling inside the hollows that transform into cavitating streaks, when the cavitation number is decreased. While the streaks are located in the grooves and do not interact with one another, the flow regime remains stable. However, when their size becomes larger than the groove diameter, they extend beyond these hollows, interact and form an entire cavity which immediately becomes unstable and starts to oscillate. At the transitional flow regime, when cavitating streaks are formed inside the grooves, the intensity of turbulent fluctuations over the modified hydrofoil surface is decreased in comparison with the regime of transient bubble cavitation. This occurs because isolated cavities inside the grooves are likely to restore the shape of the modified foil, making the geometry of its surface closer to the original profile. Thus, the grooved section takes on a streamlined body shape due to local cavitation in the hollows. Besides, the grooves on the GV2 surface cause local flow turbulization in the near-wall region, which seems to be the reason of the delay in cavitation evolution on the grooved hydrofoil. In general, the grooves on a hydrofoil surface are capable to hinder the cavitation development to some extent and prevent the transition to unsteady flow regimes.