Tetraquarks with colour-blind forces in chiral quark models

We discuss the stability of multiquark systems within the recent model of Glozman et al. where the chromomagnetic hyperfine interaction is replaced by pseudoscalar-meson exchange contributions. We find that such an interaction binds heavy tetraquark systems QQ \bar q \bar q (Q = c,b and q = u,d) by 0.2-0.4 GeV. This is at variance with results of previous models where cc \bar q \bar q is unstable