All but six complied with the law, with 20 per cent of Wellington and Hutt Valley retailers failing to ask for identification, and other breaches in Whanganui.
The offending premises had all received education visits before the controlled purchase operations which made their breaches more disappointing, a Ministry of Health representative said.
"Generally the results of retailers visited across the lower North Island were excellent and highlight the awareness of compliance among tobacco retailers of the Smokefree Environments Act 1990," the representative added.
Tobacco Control Purchase Operations monitor the level of compliance by tobacco retailers with the Smokefree Environments Act requirement that no tobacco products be sold to any person under 18. Any breaches of this act can result in an instant fine of up to $1000.