Gardaí identify a suspect in more than four out of five drugs cases, but fail to detect an offender for the majority of sex offences.
Figures released by the CSO on detection rates based on the Garda's PULSE system, also show that while most crimes are committed in Dublin, the fewest are detected in the capital.
A crime is considered detected when gardaí have identified and sanctioned a suspected offender for the crime.
The CSO figures show that gardaí identify a suspect in 87% of drugs cases, but only in 12% of sexual offence cases, which is, however, a slight improvement on the year before.
In two thirds of homicide cases, which include manslaughter and murder, an offender is identified.
Detection rates are also high at over 80% for public order and related offences, but relatively low for burglary and damage to property - at 14% and 20% respectively.
The CSO said An Garda Síochána's detection rates for 2019 are broadly similar to those for the previous year with more people caught for crimes outside the capital.
It added that detection rates tend to increase over time as more investigations are concluded.