A process to prepare a cyclic polyester oligomer composition having a cyclic polyester oligomer having furanic units, includes the step of reacting a monomer component, for example, 2,5-furan dicarboxylic acid and, for example, ethylene glycol, in a ring closing oligomerization at a reaction temperature and reaction time, for example, at 100° C. to 350° C. for 30 to 600 minutes to obtain a cyclic polyester oligomer having furanic units. The process yields a cyclic polyester oligomer composition which can be used in further ring-opening polymerization reactions to produce a polyester polymer. The cyclic polyester oligomer composition has a cyclic polyester oligomer having furanic units and less than 5% linear oligomeric polyester species in the composition.