In first aid trainng CPR is the area of most change and probably most research. The Amercian Heart Association issued on 31st March 2008 new guidelines aimed at the layperson. Details can be found here, but essentially a bystander witnessing a sudden collapse in an adult is recommended to only perform chest compressions.

This has lead to the European Resuscitation council issuing its own statement not altering its existing advice, click here for a PDF version. So for us as a UK based training company, until told otherwise its still 30 compressions followed by 2 ventilations.

If a rescuer is unwilling or unable to perform ventilations "hands only" CPR would be better than no CPR.