The electrical properties of nanostructured delta-Bi2O3 and doped Bi2O3 thin films are studied using electrochemical impedance spectroscopy. Firstly, it is shown that films presenting the cubic fluorite Bi2O3 phase can be stabilized in a wide temperature range by adding dopants; from room temperature to 300 degrees C for Al, 500 degrees C for Ta and 600 degrees C for W. An enhancement in the total mixed conductivity of about three orders of magnitude is obtained for the Al-doped films and only of two orders of magnitude for the other dopants in the low temperature range (100-250 degrees C). Impedance analyses suggest that the conductivity is predominantly driven by delocalized ion conduction occurring through the abundant grain boundaries of the nanostructured thin films.