The arrests came as two teenage boys, who were headed in the direction of the festival, were taken to Westmead Hospital after a suspected drug overdose.

Paramedics were called to the boys who were travelling on a private bus on the M2 motorway at Seven Hills.

Another three people at the festival were taken to hospital after having adverse reactions to drugs and 116 people were treated at the festival by paramedics.

Police said they arrested 116 people who were allegedly found in possession of illicit drugs and 13 people were charged with drug supply offences.

Three people were charged with assault, another three were arrested for allegedly assaulting police and six people were charged with resisting police in the execution of duty.

As a crowd of more than 25,000 people enjoyed the music festival, officers from the public order and riot squad, the dog unit and mounted unit patrolled the event.

Despite the number of arrests, Superintendent Karen McCarthy said she was happy with the overall behaviour of attendees.

"Most of the festival goers were able to enjoy the featured acts safely and without the dangerous effects of illicit substances or anti-social behaviour," Superintendent McCarthy said.

"People need to realise that high-visibility police operations are par for the course at major music festivals. If you bring illicit drugs to these events, chances are you will be caught.

"The organisers put together a well-run event and we will continue to work with them in the future to help ensure music-lovers can attend in a safe, drug-free environment," she said.

The Sydney Morning Herald