She has promised a renewed crackdown on organised crime after revealing that drugs worth more than €11m have been seized in the past month.
She said that was a very substantial amount and included heroin, cocaine, ecstasy and cannabis.
A significant number of firearms, including some very high calibre weapons, had also been confiscated.
She described the seizures as proof of the garda determination to focus on drugs and organised crime.
“We are relentless in our pursuit of people, many of whom are commodity brokers, who also smuggle cigarettes and firearms as well as drugs,” she added.
Ms O’Sullivan made her comments in Killarney yesterday where she addressed delegates at the annual conference of the Garda Representative Association for the first time.
Earlier, association president John Parker had claimed that for each of the substantial seizures, similar shipments had slipped through the net because of a lack of boots on the ground.
But Ms O’Sullivan said the gardai had very dedicated resources committed to tackling drugs crime and would continue to focus on it.
Almost half of the monthly total of seized drugs was recovered by members of the garda national drugs unit in a major operation in counties Dublin and Meath.
Hauls of drugs were found in storage depots in Navan and Finglas and two other locations in the capital while guns, including a Steyr machine gun pistol, were also confiscated.
O’Sullivan also pledged that the force’s firearms response capability would be kept under constant review.