Based upon literature and personal experience the authors review radiological techniques of evaluating colonic transit time in functional disorders of the large intestine. The distribution of given per os markers in the whole colon indicates prolonged transit time, which takes place in constipation of colonic inertia type. In the case of markers accumulation in the distal segment of the large intestine we encounter functional constipation of outlet obstruction type. The authors believe that colonic markers studies, easy to perform and non invasive for the patient should be carried out in order to obtain full information about defecation disorders.