Smokers should be more alive than others to dangers of high blood pressure. But the problem is picked up less in them, leaving them vulnerable to major complications.
The study at the University College took data from the Health Survey for England in 2003 and 2006 and found it was being detected less frequently in people who smoked compared with those who did not, or those who used to smoke but had quit.
AdvertisementOne reason for the lack of diagnosis could be that smokers in the study tended to be thinner than those who did not smoke.
On the other hand improvements were detected over time in the proportion of people who knew they had high blood pressure.
The researchers at the University College, London, who were funded by Cancer Research UK, said that GPs may be more likely to test blood pressure in people who were overweight.
Since 2004, GPs have been paid an incentive to test blood pressure and to record whether someone is a smoker.
Smoking and high blood pressure, also known as hypertension, are both key causes of early death, the researchers wrote in the European Journal of Cardiovascular Prevention and Rehabilitation.
National guidelines advocate that doctors encourage those with high blood pressure to stop smoking and that greater effort should be made to look for signs of the condition in those who smoke.
Study author Dr Jennifer Mindell said it was disappointing to find smokers with high blood pressure were not being diagnosed.
''It's important to pick up high blood pressure in everybody but it's particularly important in somebody who already has a higher than average risk of heart disease or stroke, including those who smoke.
''And anything that gives people additional motivation to quit must be a good thing.
''It is a reminder for GPs that measuring blood pressure in smokers, even if they are thin, is important.''
June Davison, a cardiac nurse from the British Heart Foundation, said: ''It is crucial that smokers are aware of their blood pressure as smoking and high blood pressure are among the most common risk factors for cardiovascular disease.
''This study also highlights that if smokers are made aware of their high blood pressure, it can increase their motivation to stop smoking.
She added that smokers over the age of 40 should go for a health check where their blood pressure will be measured and advice on quitting smoking can be given.