Angular size in "quintessence" cosmology

We investigate the influence of an exotic fluid component ("quintessence") on the angular size-redshift relation for distant extragalactic sources. Pa rticular emphasis is given for the redshif z(m) at which the angular size t akes its minimal value. We derive an analytical closed form which determine s how z(m) depends on the parameter of the equation of state describing the exotic component. The results for a flat model dominated by a "quintessenc e" are compared in detail with the ones for the standard open model dominat ed by cold dark matter. Some consequences of systematic evolutionary effect s on the values of z(m) are also briefly discussed. It is argued that the c ritical redshift, for all practical purposes, may completely be removed if such effects are taken into account.