This study is a corpus-based constructionist analysis of Old English (OE) constituent order, focusing on verb-initial declaratives and þa-VS main clauses. The main objective of the investigation is to determine the degree of the formal and functional similarity of both patterns in order to establish whether they functioned as two independent constructions (in Construction Grammar terms), with their relation based on functional contrast. The other possibility taken into consideration in the analysis is that the two patterns should rather be treated as variants of the same construction, as suggested in some previous, non-constructionist studies of the topic, which would make it possible to analyse them as allostructions. The study shows that on the general level of the language network, the two clause types are surprisingly different in many respects: their form is less similar than previously assumed, they have drastically different corpus distributions, they show different collocational preferences and perform different discourse functions. Nevertheless, on the lower level of the network, the two constructions show some overlaps in the presentational, narrative and reporting function. At the same time, however, there is a deep functional difference between texts authored by Ælfric and other OE prose records.