Surface X-ray diffraction experiments have been performed on the K-induced super structures on Ag(00 1). Both, the (2 Γ 1) and the (3 x 1) superstructure which are formed at K-coverages of about 0.15 and 0.30 ML, are found to consist of missing row type reconstructions, where one and two Ag-rows are missing along [1 T 0], respectively. In both cases the K-atoms reside within the large grooves of the missing row structures. For the (2 x 1) structure we find the K-atoms adsorbed on bridge sites relative to second-layer Ag-atoms, thereby coordinated by six Ag-atoms (four first-layer Ag-atoms and two second-layer Ag-atoms) at a distance of 3.44 (5) A. The consideration of anharmonic displacement factors for the top layer Ag atoms is necessary for the proper description of the structure, leading to a significant better agreement with the data as compared to pure harmonic refinement as expressed by the goodness of fit parameter (GOF = 0.93 versus GOF = 1.67). Allowing for anharmonic displacement parameters we determine a Ag interlayer spacing dl 2 which is contracted relative to the bulk spacing by only 3.2% instead of 12.7% if anharmonic contributions are neglected. In the (3 Γ 1) superstructure the K-atoms form staggered double rows along [1 I0], in this way forming a distorted quasihexagonal ovoerlayer. The K-atoms are located close to bridge sites to second layer Ag-atoms at a minimum distance of 3.55 (5) A. Additional defects are found in the first Ag-layer. For this more open reconstruction the Ag-interlayer spacing, dl 2, is contracted by about 10% confirming recent investigations on ECC (l 1 0) surfaces regarding the polarization-induced compression of the interlayer distances.