There are up to 180 crime gangs in Northern Ireland engaged in lucrative activities such as counterfeiting and fuel smuggling, police have said.
A significant minority have or had ties with paramilitaries, Chief Superintendent Roy McComb added.
They deal in whatever commodity they can make money from and have ties with other parts of the UK and Ireland, Stormont's Justice Committee heard.
Mr McComb and other experts in organised crime have given evidence to the committee.
"The number of crime gangs that we have identified moves around, it is a reasonably fluid amount, somewhere between 160 and 180 crime gangs," he said.
"That is 160 crime gangs in Northern Ireland, the majority did not do single crime types, the majority do multiple crime types. Crime gangs are in the business of making money. Anywhere they can make money they will move towards."
The gangs cooperate for commercial gain, they never work in isolation and are always connected to somewhere else, the committee heard.
Mr McComb said a "healthy minority" of the crime gangs had paramilitary links, but SDLP North Belfast MLA Alban Maginness expressed concern.
"Paramilitary-related gangs are making money for themselves and their capacity to make money gives them the capacity to buy arms, munitions and explosives that create terror in this community. It disturbs me that there is this significant minority within the gangs you are talking about," he said.
Mr McComb said cooperation between the PSNI and Garda had never been better during his 20 years in policing. The number of arrests by the PSNI for drugs has increased substantially from 2003 with the number per quarter rising from 350 to 590.