In the last decade, soil quality indicators have become a big issue in soil research. Indices have been proposed mainly based on soil biological activity, soil chemical characteristics and hydrological parameters. Soil micromorphology, despite its very high research potential, has not produced a large effort on this topic. This work attempts to give a contribution to soil physical quality evaluation using image analysis of the soil pores. There are different image analysis measurements such as pore size, feret diameters, perimeter, area, number of holes, length-width projections; circularity, connectivity, etc. Between the different measurements, Pore Size Distribution (PoSD) is possibly the simplest and most useful. Indeed it provides fundamental information about the soil structure and directly affects soil hydrological behavior. Two soil structure quality indices, FFTI and TMI, based on the analysis of the PoSD diversity are proposed here: the first based on spectral decomposition (in the frequency domain) of the PoSD by FFT (fast fourier transform); the second is derived from the analysis of the manifold mode values generally showed in PoSDs. Reliability and effectiveness of those indices have been tested applying them to four case studies on different agricultural practices: application of organic fertilisers, intensive tillage against no tillage on fragile environment (Terra Rossa), different irrigation systems and use of saline water. Comparison with indices, recently introduced, resulting from hydrological analysis has been also performed. Results demonstrate that FFTI and TMI are good indicators of soil quality confirming the great relevance and potentialities of pore image analysis to evaluate soil structure.