He composed, about the year 1335 (as Bishop Beveridge satisfactorily makes out from the author's own enigmatical statement) an alphabetical compendium of the contents of the genuine canons. It was intended to supply a more convenient repertory for ordinary use than was furnished by the collections of Photius and his commentators. The letters refer to the leading word in the rubrics of the titles, and under each letter the chapters begin anew in numerical order. In each chapter there is commonly an abstract, first of the ecclesiastical, then of the secular laws which relate to the subject; but the sources whence the secular laws are cited are not ordinarily referred to, and cannot always be determined. The ecclesiastical constitutions are derived from the common canonical collections. This compilation, as the numerous extant manuscripts prove, became very popular among ecclesiastics. The preface to the of Blastares contains some historical particulars, mingled with many errors, concerning the canon and imperial law. As an example of the errors, it may be stated that the formation of Justinian's Digest and Code is attributed to Hadrian.

In most MSS. a small collection of minor works, probably due to Blastares, is appended to the Syntagma. As to unpublished works of Blastares in MS., see Fabric. Bibl. Graec. xii. p. 205.

At the end of the Père Goar's edition of Codinus is a treatise, written in popular verses (πολιτικοὶ στίχοι), concerning the offices of the Palace of Constantinople, by Matthaeus, monk, Δύτης, and physician. The author may possibly be no other than Blastares.