This work presents the new observations of structures and phase transitions of the Pb/In/Si(111) adsorption systems for lead deposition on the Si(111)-√7 × √3-In reconstructed surface. Using Low Energy Electron Diffraction and X-ray Photoelectron Spectroscopy several surface structures like 1 × 1, 4 × 1 as well as some characteristic features of 3D Pb(111) islands have been distinguished. It was noticed that the 4 × 1 phase is induced only when the In/Si(111) surface is initially covered with sufficient amount of lead and after sample annealing at elevated temperature.