The objective of this paper is to highlight the results and experiences obtained by the Petroleum Company of Venezuela (PDVSA) as a result of the changes applied to the displacement systems in liners, for the cementing of intermediate and production strings in the deep wells of the North Monagas area, located in Eastern Venezuela. In the year 1998, there was a 24% drop in the success rate of liner cementing during the well construction process. This resulted in the execution of 11 repair jobs having to be performed to correct primary cement job failures, with an associated cost of US $370,000. Based on an analysis of the execution and evaluation of the said jobs, it was determined that the most recurrent problems were flaws in the displacement system with the different types of hangers used. As a consequence, a more detailed analysis was done which allowed the identification of the most common causes when the failures occurred, such as: the piston effect between the liner displacement plug and the seal bore, and inadequate sealing during the latch-in of the plugs. As a result of the optimization proposals and changes made to the designs in liner hangers used for cementing 7 5/8 inch intermediate and 5 ½ inch production strings, a 22% increase in the success rate was achieved compared to 1998, thus reducing the percentage of repairs to primary cement jobs due to failures in the liner hanger to just one from a total of twenty seven (27) jobs performed in the period 1999-2000. By these changes, a total of US $1,500,000 in additional costs for repairs to primary cement jobs was avoided.