Levels of tar in some brands of tobacco are up to 15 times higher than in others, according to laboratory tests quoted by the Consumer Council yesterday.
Tests on 84 cigarette brands found them all to be within the legal limit of 17 mg of tar per cigarette, though one brand, Pine Prime, which had the highest amount of tar, contained 15 mg per cigarette.
Experts warned even a low amount of tar could damage the health of smokers.
"Do not think that it is safe to smoke a cigarette with lower tar," a specialist in respiratory medicine, Dr Leung Chi-chiu, said.
"The composition of tar is very complicated. Even if the overall amount of tar is low, it may contain a very high level of cancer-causing substances."
Tar is produced when organic material such as tobacco decomposes at high temperatures.
Leung said it was not possible to block tar completely, even if a smoker used a filter.
"Of course it is more dangerous if the cigarette has a very high level of tar," he said.
The latest edition of the council's magazine, Choice, cites results of government laboratory tests showing significant differences in tar levels between different brands of tobacco.
Marlboro Black Menthol One, Pianissimo Menthol One and Virginia Slims Menthol Rose, all had the lowest level of 1mg of tar per cigarette.
Pine Prime, made in Korea, had the highest level of 15mg of tar per cigarette, followed by the United States' Philip Morris Menthol, Hong Kong's Good Companion Deluxe and China's Wuyeshen, all with 14mg.
The average level of tar among all the brands tested was 8.4 mg per cigarette.
The level of the addictive substance nicotine detected in the tobacco samples in the December 2013 tests ranged from 0.1 to 1.2 mg per cigarette.
The watchdog warned that electronic cigarettes, which contain nicotine but not tar, are not necessarily a healthy alternative to traditional cigarettes containing tobacco.
While brands of electronic cigarettes feature various concentrations of nicotine, the World Health Organisation has questioned the safety of the devices, warning that inhaling an excessive amount of nicotine is also dangerous.
Leung said there was scientific evidence to suggest that nicotine could affect both the central nervous system and blood vessels.
There was also a report suggesting it had mood-altering effects, he said.
The substance, found in plants, is the primary addictive agent in cigarettes and is considered a stimulant.
Leung added: "Combining the two substances tar and nicotine together has a more damaging effect on health."