It is hoped the money will relieve the postcode lottery in access and go some way to meeting the expected quadrupling in demand for scans by 2008.
While PET (positron emission tomography) scans are traditionally used for bowel and lung cancer, there is also evidence they are effective for head and neck cancers.
Just over 10,000 scans are carried out each year, but within three years the figure could reach 40,000. The rest of the demand is expected to be met by the private sector.
Unlike other diagnostic equipment waiting times are not a problem where the scanners are available. In some areas of London patients only have to wait a week.
But with all but one of the seven scanners in England based in the south east, patients in the north of the country are often not even referred for a scan.
It is not clear how many new scanners the extra money will pay for as it has not been decided what proportion of fixed and mobile scanners should be ordered and where they should be based.
Health Minister Rosie Winterton said: "The NHS Cancer Plan is delivering results - more investment and more staff have led to cancer death rates falling across the board. However, we need to do more to speed up treatment even further.
"This new equipment will provide thousands of extra scans. Investment in scanning facilities will mean faster treatment for patients in locations where they are most needed."
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