Since Parnassos Mt. has been uncontrollably exploited by intense human intervention throughout the years, large areas are highly degraded, and much too often the bedrock and rocky outcrops are the dominant feature of the landscape. This vegetation is the legacy of the one that, according to Homer, was once so dense that neither the sun nor rain could penetrate it.

Under the influence of biotic and abiotic factors, plant species establish specific vegetation zones (Dafis 1972). On Parnassos Mt. are found:

- the non- forested zone of high mountains (Astragalo-Acantholimonetalia) with the Astragalo –Daphnion alliance
- the beech- fir zone (Fagetalia) with the Abietion cephalonicae alliance, including not only Abies cephalonica forests, but Pinus nigra clusters as well
- the deciduous broadleaf zone (Quercetalia pubescentis), including deciduous forests as well as kermes oak brushlands
- the coastal, hill & submountain zone (Quercetalia ilicis) is fragmented, limited to small spots, including broadleaved evergreen thickets of Oak and Pistacia lentiscus trees.
- the riparian ecosystems, appearing mostly along the river margins and banks

Low vegetation above the treeline (non- forested zone of high mountains)
This kind of vegetation begins from the upper limits of the fir forests and reaches up to the top of Parnassos Mt. (Liakoura 2,457 m). The common vegetation here is shrub, phryganic, and herbaceous species. This zone’s vegetation is highly degraded, mainly due to the intense grazing. The main species encountered are the following:

At the lower limits of this zone scattered Juniperus foetidissima individuals are found, generally in poor condition and small height.

High arboreal vegetation
It starts from the lower limits of the previous zone (1800m) and goes down to 600m. This zone includes Abies cephalonica, Pinus nigra and deciduous oak forests.
Abies cephalonica forests:
The fir forests on Parnassos Mt. reach up to an altitude of 1.700 - 1.800m. There, they form the treeline that comes in contact with the sub (pseudo-) alpine meadows and descend to an altitude of approximately 600m.
The current upper limits of fir forests are such due to purely anthropogenic influence and not to bioclimatic reasons. On the other hand, fir expands its presence to lower altitudes occupying the spreading of Quercetalia ilicis zone.
Thus appear the following plant formations:
-Fir forests with the presence of Quercus frainetto
-Fir forests with the presence of species of the alliance Osrtyo-Carpinion and Quercion frainetto (Tilio-Castaneum)
-Fir forest of Quercion ilicis
Pinus nigra forests:
The black pine forests on Parnassos Mt. form mixed populations with Fir at an altitude of about 750m., reaching up to about 1.500m.
Deciduous Oaks Forests:
Most of the area of the deciduous oaks forests has been occupied by Fir and Kermes Oak. However, after sharp declines in livestock and better protection of the area, oaks (Quercus frainetto and Q. Pubescens) are being re-established.
Remarkable is the discovery of a sparse cluster of several dozen acres of Quercus ithaburensis subsp. macrolepis, at an altitude of 850-900m.

Shrubby vegetation
Mediterranean shrublands with domination of Quercus ilex
Quercus ilex is found sparsely only on the north side of Parnassos Mt., at the lower treeline of Abies cephalonica, in moist places. Its presence is significant at the rocky slopes of the ravine east of Tithorea (Velitsa), most often in contact with the Fir forest.
Shrublands with Quercus coccifera
Quercus coccifera shrublands is the second largest plant cover area, after A. Cephalonica forests, on Parnassos Mt. The species occurs in areas with the lowest elevation and reaches up to the Corycian Cave (about 1.400m altitude) at all types of soil.
Mediterranean shrublands with domination of Pistacia lentiscus
Pistacia lentiscus shrublands are encountered above the Amfissa valley and up to an altitude of about 500 - 550m. These shrublands are highly degraded and fragmented with frequent presence of brushwood.

Riparian Ecosystems
The dominant species of these ecosystems is Platanus orientalis, found at an altitude of up to 1.000m on Parnassos. At about the same altitude at the Eptalofos stream, Salix elaeagnos is also recorded, whereas at lower altitudes Nerium oleander, Vitex agnus-castus, Arundo donax, Salix alba, Alnus glutinosa, Tamarix smyrnensis and Phragmites communis appear.