The Deputy Prime Minister will highlight problems in North Ayrshire, Clackmannanshire and West Dunbartonshire, alongside 17 other parts of the UK.
Young people in these areas will get help sooner to get into the workplace and off benefits, he will announce.
But Labour said the plans were "too little too late".
In a speech today, Mr Clegg will warn that youth unemployment will not automatically recover alongside the wider economy.
He will say: "If we pin all our hopes on youth unemployment disappearing once growth returns we'll be sorely disappointed."
He will also single out the former Labour leadership contender, Mr Miliband, for praise for his attempts to boost youth employment and his identification of so-called "hotspots".
Mr Clegg will say that the areas highlighted were diverse, but they all share one characteristic.
"Maybe inner city areas with high levels of disadvantage, rural communities where businesses are struggling to take people on, former mining towns at the sharp end of industrial decline.
"Whatever the reason, these are the toughest parts of the country to be young, down, and out," he will say in the speech.
The 20 areas identified have the highest rates of long-term youth unemployment and the lowest rates of return to work.