Nearly 550 motorists were arrested after failing drink or drugs tests over the Christmas period.
The all-Wales Christmas drink and drug driving campaign saw 7,671 tested between 1 December and 1 January.
South Wales Police tested the most - more than 3,500 - with 179 alcohol arrests, while North Wales Police made the most drug-related arrests with 84.
Dyfed-Powys Police had the highest proportion of arrests to tests while the Gwent force tested the fewest.
Supt Jane Banham, of the North Wales Police Roads Policing Unit, which led the campaign, said: "A notable difference for us in north Wales during this campaign is that there have been more drivers who have tested positive for drugs than alcohol.
"Whilst this is a concern, it is a reflection of our ability to carry out roadside tests for cannabis and cocaine.
"I don't think people are quite grasping the full extent of the danger drug-driving poses."
The force said last year people driving under the influence of drugs was becoming as common as drink driving.
In the 2018 campaign, the total number of people arrested for providing a positive alcohol breath test, refusing or failure to provide a sample was 368.
There were 179 arrests for drugs.
The overall figures represent a rise on 2017. However, those statistics did not include details from Dyfed-Powys Police.
Teresa Ciano, chairwoman of Road Safety Wales, said: "Unfortunately, some people are still willing to put themselves or innocent road users at risk and only really learn the consequences of their actions if they're caught by the police or are involved in a life-changing collision.
"We'd like to remind people that it makes no difference if you drink cocktails in a sophisticated wine bar with friends or cheap beer at home on your own; if you drive after consuming alcohol the penalties are the same."