  We have developed a theory for inhomogeneous systems that allows for
incorporation of effects of mesoscopic fluctuations. A hierarchy of equations
relating the correlation and direct correlation functions for the local excess
$\phi({\bf r})$ of the volume fraction of particles $\zeta$ has been obtained,
and an approximation leading to a closed set of equations for the two-point
functions has been introduced. We have solved numerically the self-consistent
equations for one (1D) and three (3D) dimensional models with short-range
attraction and long-rannge repulsion (SALR). Predictions for all the
qualitative properties of the 1D model agree with the exact results, but only
semi-quantitative agreement is obtained in the simplest version of the theory.
The effects of fluctuations in the two considered 3D models are significantly
different, despite very similar properties of these models in the mean-field
approximation. In both cases we obtain the sequence of large - small - large
compressibility for increasing $\zeta$. The very small compressibility is
accompanied by the oscillatory decay of correlations with the correlation
length orders of magnitude larger than the size of particles. Only in one of
the two considered models for decreasing temperature the small compressibility
becomes very small and the large compressibility becomes very large, and
eventually van der Waals loops appear. Further studies are necessary to
determine the nature of the strongly inhomogeneous phase present for
intermediate volume fractions in 3D.
