This paper identifies the most relevant diagnostic elements that Mexican consultants use in order to know the current performance of micro, small and medium size enter prises (MSME) prior to a quality practice implementation and to estimate the probability of success of their intervention. In order to obtain the diagnostic basic elements we employed a web–based survey. In grouping of the diagnostic elements Howard and Associates integrated organizational diagnosis model, factor analysis and cluster analysis were used. Thirty four diagnostic basic elements and seven diagnostic categories were identified. We find about 90% of the consultants had made successful implementations in most of the times (75% to 100%) when using diagnostic elements.