  In this paper we consider description of kaon -- anti-kaon interference in
the context of a theory with deformed $\cal CPT$ symmetry. In the case of such
theoretical models, deviations from the standard $\cal CPT$ invariance is
related to the momentum carried by the particles; in particular the rest masses
of particles and antiparticles are equal. We find that the decay intensity of
kaon -- anti-kaon pair has three contributing terms: the correct-parity, the
wrong-parity, and the interference between them, all of which are affected by
deformation. Using the fact that the presence of such terms were not observed
we estimate the magnitude of deformation parameter $\kappa \gtrsim 10^{18}$
GeV, very close to the expected Planck mass scale. This raises hopes that the
effect, if exists, could be detected in a near future accelerator experiments.
An uncertainty of the energy measurement is crucial for accuracy of these
predictions.
