The electrochemical porous etching of n-InP in 1 M HCl has been investigated by monitoring the mass of In 3+ released during and after the anodic polarization. The study has been performed on both crystal-oriented (CO) and current line-oriented (CLO) pores grown at 10 mA·cm −2 and 5 V vs Ag/AgCl. An unexpected evolution of the mass of In 3+ has been measured when the electrochemical dissolution process is stopped. It indicates a mass loss more than twice higher after 2 or 3 hours. This demonstrates that the accurate amount of dissolved InP must be considered a longtime after the end of the polarization. The comparisons of the etched masses for CO and CLO pores with the values calculated from the coulometric charges indicate that the etching processes are similar for the two pore geometries and that the dissolution valence for InP is 2. The chemical analyses, performed by X-ray photoelectron spectroscopy, reveal that the main corrosion products are Cl-containing compounds such as InCl 3. This gives valuable information to confirm an InP porous etching mechanism proposed earlier in literature.