The cross sections fo the dijet production in diffractive deep-inelastic scattering are calculated for the first time in next-to-next-to-leading accuracy.
The next-to-next-to-leading order corrections are found to be positive and sizable.
The cross sections are compared to a considerable number of HERA measurements performed by H1 and ZEUS collaborations. We observe an overall good agreement of the next-to-leading order calculation with data, whereas the next-to-next-to-leading calculations tend to overestimate the data, probably due to poorly constrained gluon component of the diffractive parton distribution functions.