Under conditions of increased tunnel current and voltage, with the electron flow directed towards the sample, nanometer‐scale structures have been written into ultrathin (∼20 nm) light‐emitting porous silicon (PS) films using scanning tunneling microscopy in a high‐vacuum environment. For the writing process, a threshold voltage of ∼4.5 V is observed and the resulting dimensions range between 20 and 50 nm. Depending on the writing parameters, the modified regions relax or remain stable during the observation time of several days at room temperature. These results can be assigned, in the first case, to a disruption of a small number of bonds, followed by reconfiguration, and a charging of dangling bond sites, followed by carrier release, in near surface regions. In the latter case, the creation of time‐stable defect states within the PS layer is proposed.