Mother will create the £1.5 million burst of ads, which will run on national radio and in the national and regional press from March to April. A second phase will run after the period when government campaigns are halted for the May local authority elections.
PHD will handle media planning and Profero will be responsible for online.
The drive will use the Government's drug awareness brand, Frank, to warn young people of the health risks of using cannabis. A second strand, aimed at adults, will remind people that marijuana is still illegal and highlight the penalties for producing, dealing in and possessing it.
Critics say the Home Office is hoping to clear up confusion surrounding its mixed messages on cannabis. Two years ago, the drug was downgraded from a class B to a class C drug.
There was speculation that the Home Secretary, Charles Clarke, would reverse the decision, but last week he announced cannabis would remain a class C drug.