Palladium thin films are object of great interest in catalysis, as well as in hydrogen sensing, storage and generation. Noble metals such as Palladium are the most effective if deposited as ultrathin films on a large surface area. Atomic layer deposition (ALD) is considered to be the method of choice to grow ultrathin films on various substrates with demanding surface topologies. This contribution will present in situ and ex situ studies of Palladium films grown by plasma-assisted ALD. The Pd films were deposited on alumina at 100ºC using Pd(hfac)2 (hfac= hexafluoroacetylacetonate) as the precursor, and H2 gas and H2 plasma as reducing agents. In situ spectroscopic ellipsometry (SE) has been used to monitor the film growth and obtain detailed information about the optical properties of Palladium. The nucleation and subsequent island growth have been characterized by Transmission Electron Microscopy (TEM). X-Ray diffraction, X-ray photoelectron spectroscopy and Rutherford backscattering spectrometry have been carried out in order to characterize the grown films. The thermal ALD process only allowed for growth of Pd on a Pd or Pt seed layer, while the plasma-assisted ALD process also led to growth on an alumina surface. In both cases the steady-state growth rate was ~ 0.17 Å/cycle as determined by in situ SE. The observed selective growth on catalytic Pd or Pt seed layer of the thermal process holds promises for nanopatterning applications, whereas the plasma-assisted process can be used to deposit Pd nanoparticles and films at low-temperature on oxide substrates, which has considerable potential for catalysis and hydrogen sensor applications.