Quantum-mechanical calculations of fully conjugated dendritic oligomers carried out at B3LYP/3-21G//HF/3-21G (d) and B3LYP/3-21G//PM3 levels of theory showed that loose dendritic architecture of β,β-dibromo-4-ethynyl styrene oligomers contributes little to the instability and conjugation disruption compared to 1→2 branched polyacetylene, while Br terminal atoms in dendrimers strongly affect the electronic density distribution in studied molecules. On the one hand the bulky bromine atoms decrease the conjugation in Br-terminated dendrimers caused by steric hindrances, on the other hand, highly polarisable bromine atoms reduced significantly adiabatic ionisation potentials (IP a ) to be up to 1.5eV lower than corresponding vertical potentials (IP v ). Another phenomenon contributing to the reducing of IP a ’s of all dendrimers is the flattening of molecular geometry accompanying the ionisation thus allowing better delocalisation of positive charge over the conjugated system while all aromatic ring except the very outer layer lost their aromaticity becoming essentially quinone by nature.