This paper  analyses the formal structures  of the first movement of two piano sonatinas, both composed in 1927, by Nikos Skalkottas and Yannis Constantinidis. Although both sonatinas are early works, they comprise compositional elements and follow techniques which were further developed by the two composers in their later works. The aim of the analysis is twofold: it considers both composers’ understanding and re-interpretation of normative formal models; and by examining those ‘constant’ structural elements of their respective style, it determines their significance as representative components in the establishment of early twentieth-century Greek modernism. The first movement  of Skalkottas’s Sonatina outlines a ternary ABA’ form. The thematic material of each section is introduced in a polyphonic, multi-layered texture. The harmonic background of the work is based on an anscending cycle of fifths and the pitch class set [0, 2, 7], which comprises two successive perfect fifth intervals. Section B introduces new contrasting thematic material, together with octatonic and whole-tone scales. In contrast, the first movement of Constantinidis’s Sonatina outlines a textbook sonata form, in particular the ‘Type 3 Sonata’ – as presented in Darcy-Hepokoski’s sonata form theory – with medial caesuras, essential expositional and structural closures, development tonal and motivic plan, re-transition, resolution and so on. The entire piece is based on the combination of two intervals, the augmented and the perfect fourth, which are integrated with the interval of a second. This combination applies to the motivic, melodic and harmonic background of the piece, which is unified by the octatonic scale, already included in the primary and the secondary thematic area. There is a resolution at the end of the piece, with the second half of the exposition transposed at the interval of a fifth.