Case dentro de un Where

[Libras]

Y si lo haces asi:
select
CASE WHEN @Mes % 2 = 0 THEN
[COLOR="rgb(65, 105, 225)"] ((@Mes = [GastosxConsorcio].[Mes] and @Anio = [GastosxConsorcio].[Anio])[/COLOR]
OR
([GastosxConsorcio].[Frecuencia] = 1)
OR
([GastosxConsorcio].[Frecuencia] = 2 and [GastosxConsorcio].[EsPar] = 1))
ELSE
((@Mes = [GastosxConsorcio].[Mes] and @Anio = [GastosxConsorcio].[Anio])
OR
([GastosxConsorcio].[Frecuencia] = 1)
OR
([GastosxConsorcio].[Frecuencia] = 2 and [GastosxConsorcio].[EsPar] = 0))
END
from [GastosxConsorcio] No te sirve??