Figures provided by an Garda Síochána to RTÉ Investigates show that 27%, or more than 1 in 4 summons for all crimes were not served in 2016.
However, this is an improvement on 2015 when 43% of summons went unserved.
RTÉ Investigates-Law and Disorder, to be broadcast on RTÉ One at 9.35 tonight, will also show that approximately 15% of drink-driving summonses do not get served.
In a statement to the programme, a spokesperson for an Garda Síochána said it "takes its role in the serving of summons very seriously" and "it recognises that further improvement is required in this area."
The spokesperson also said "There are a number of reasons summons are not served that are outside of our control" such as people who "are operating with multiple identities; people deliberating evading being served with a summons; people moving and not providing a forwarding address"
