  Recently Gaiotto [1] considered conformal defects which produce an expansion
of infrared local fields in terms of the ultraviolet ones for a given
renormalization group flow. In this paper we propose that for a boundary RG
flow in two dimensions there exist boundary condition changing fields (RG
defect fields) linking the UV and the IR conformal boundary conditions which
carry similar information on the expansion of boundary fields at the fixed
points. We propose an expression for a pairing between IR and UV operators in
terms of a four-point function with two insertions of the RG defect fields. For
the boundary flows in minimal models triggered by \psi_{13} perturbation we
make an explicit proposal for the RG defect fields. We check our conjecture by
a number of calculations done for the example of (p,2)--> (p-1,1)+(p+1,1)
flows.
