The first comprehensive investigation of Montpellier maple (Acer monspessulanum L.) honeydew (HD)-to-honeydew honey (HDH) transformation pathway was performed. A leafhopper Acericerus heydenii excreting honeydew on A. monspessulanum is reported for the first time. FTIR-ATR revealed predominating sucrose and glucose in HD unlike melezitose-rich honeydews from aphids and scale insects. Octanal and nonanal were found among the major compounds of HD and HDH by HS-SPME/GC-MS. USE and HDLLE/GC-MS in HDH determined variety of present higher aliphatic compounds and minor phenylpropanes abundance. HD contained (determined by UHPLC-DAD-QqTOF-MS) flavonoid glycosides and flavonoid galloyl glycosides quercetin and isorhamnetin derivatives that along with ellagic and protocatechuic acids are common for Acer leaves. HDH was dominated by the corresponding flavonoid aglycons of quercetin and isorhamnetin indicating the glycosides hydrolysis pathway. HD and HDH both contained protocatechuic acid, ellagic acid, lumichrome and abscisic acid, and traces of apigenin.