Part I of this review considers the outcome of different methods of observation of active regions at mm- and cm-v/aves exploring the source structures and parameters in the chromosphere and corona. Calculations of emission models invoking bremsstrahlung and gyromagnetic radiation are summarlzed applying for a great
variety of physical conditions. Diagnostic capacities of different kinds of microwave burst emission are briefly taken into account.
Part II of the review considers the dm- and m-radio spectral observations as diagnostic tool for the determination of plasma parameters in the coronal parts of solar active regions. The main attention is devoted to the radio diagnoetics of solar flares. The most important types of dm- and m-radio bursts are presented.
the latest theoretical and observational results summarized and their diagnostic aapects briefly discussed.