In Acton, west London, Downing will develop an 80,000 sq ft scheme featuring 184 studio apartments in two seven-storey towers worth £25m.
The Cambridge scheme is worth £65m and will provide 586 student beds across three new buildings.
Downing’s in-house contracting division, George Downing Construction, will begin work on the Acton scheme this month, for completion in September, 2013.
Downing expects to complete the site deal in Cambridge by November, with work on the scheme starting next year.
Paul Houghton, Downing development director, said: “These acquisitions mark a significant milestone in our strategy to bring the Downing brand of superior, sustainable and energy-efficient buildings to the UK’s major student centres.
“The new funding environment and growing demand for higher quality living spaces with more amenities and better locations means student accommodation is playing an increasingly important role in how universities attract fee-paying students.”