Irregular bridges have more complex behavior than regular systems, so more details could be developed in its analysis, design and in inspection and maintenance programs. In this paper the influence of irregular conditions in substructure of bridges is evaluated by means of a parametric study, varying the height of piers. To do this, monolithic, simple-supported and continuous regular and irregular bridges were subjected to seismic action, using an accelerogram database. Elastic and nonlinear analyses were accomplished and the normalized differences between regular and irregular models were evaluated. Results indicate which irregular substructure conditions generate more vulnerable systems. Based on the obtain results, a simplified evaluation of substructure irregularity, to be used in an inspection method, is proposed.