By using Riemann--Hilbert problem based techniques, we obtain the asymptotic
expansion of lacunary Toeplitz determinants detNβ[cβaββmbββ[f]] generated by holomorhpic symbols, where βaβ=a (resp. mbβ=b)
except for a finite subset of indices a=h1β,β¦,hnβ (resp. b=t1β,β¦,trβ). In addition to the usual Szeg\"{o} asymptotics, our answer involves a
determinant of size n+r.Comment: 11 page