In the paper the authors present an analysis of two possible causes of cracking in a two-span continuous road viaduct: secondary moments and irregular  settlement. In the presented example the value of secondary moments was over three times higher than the value of moments resulting from prestress. The calculated difference in settlement between the abutment and the pillar reached over 1,5 cm.That causes an additional bending moment, which is responsible for tension in the bottom part of the beamnear the intermediate support. If those effects where not considered properly during the design stage, they may have led to cracking in the part of the structure, which is nominally in compression. Keywords: prestressed concrete; cracking; secondary moments; irregular settlement.