Healthy eating and exercise rates are up, as is vaccination. There is even some hope childhood obesity and excess weight could be on the way down, the 2014 the chief health officer's report into the health of children and young people found.

Chief health officer Kerry Chant said it was estimated less than 27 per cent of children were overweight or obese, compared to about a third in 2012.

"We may be seeing signs of a decline, but we don't want to over-sell it yet," she said. "There is no room for complacency in the areas of reducing obesity rates, soft drink and junk food consumption, TV and computer screen time."

The report found about 40 per cent of children aged between two and 15 drank at least two cups of soft-drink, cordial or sports drink a day, and one in five drank six or more cups.

And while screen time and physical activity have improved, the vast majority of kids are still spending too much time sitting and not enough time doing vigorous physical activity.

While the report found little difference between socio-economic groups when it came to weight, it appears children from wealthier backgrounds do slightly less physical activity but have more screen time, whereas among children from poorer backgrounds this pattern is reversed.

Smoking among people in their late teens and early 20s also remains high, at about 17.8 per cent. That is above the state-wide average of 16.2 per cent.

"These smoking rates are still quite troubling – we still need to drive tobacco smoking much lower than we have," Dr Chant said. "Particularly among the Aboriginal population smoking rates are incredibly high, and very concerning".

Nearly 50 per cent of Aboriginal mothers still smoke while pregnant – meaning their babies are at higher risk of problems such as sudden infant death and small birth size – along with one in 10 non-Aboriginal mothers.

However, high immunisation rates have seen a "marked decline" in children needing hospital treatment for vaccine-preventable disease, and a four-year-old Aboriginal child is now more likely to be fully vaccinated than a non-Aboriginal child (94 per cent compared to 92 per cent).

Alcohol and drug use is also down among children and young people, and children may be delaying starting drinking until older ages.

Child health at a glance:

• Only one in four kids does the recommended physical activity outside of school.
• Nearly 96 per cent of two to eight-year-olds eat enough fruit, compared to fewer than half of nine to 15-year-olds.
• One in 20 kids aged under 15 experienced 'food insecurity', when their family ran out of food and could not afford to buy more.
• Less than 61 per cent of kids aged 12-15 have tried alcohol.