Antagonists of the adenosine receptors (A<sub>1</sub> and A<sub>2A</sub> subtypes) are widely researched as potential drug candidates for their role in Parkinson's disease-related cognitive deficits (A<sub>1</sub> subtype), motor dysfunction (A<sub>2A</sub> subtype) and to exhibit neuroprotective properties (A<sub>2A</sub> subtype). Previously the benzo-α-pyrone based derivative, 3-phenyl-1H-2-benzopyran-1-one, was found to display both A<sub>1</sub> and A<sub>2A</sub> adenosine receptor affinity in the low micromolar range. Prompted by this, the α-pyrone core was structurally modified to explore related benzoxazinone and quinazolinone homologues previously unknown as adenosine receptor antagonists. Overall, the C2-substituted quinazolinone analogues displayed superior A<sub>1</sub> and A<sub>2A</sub> adenosine receptor affinity over their C2-substituted benzoxazinone homologues. The benzoxazinones were devoid of A<sub>2A</sub> adenosine receptor binding, with only two compounds displaying A<sub>1</sub> adenosine receptor affinity. In turn, the quinazolinones displayed varying degrees of affinity (low micromolar range) towards the A<sub>1</sub> and A<sub>2A</sub> adenosine receptor subtypes. The highest A<sub>1</sub> adenosine receptor affinity and selectivity were favoured by methyl para-substitution of phenyl ring B (A<sub>1</sub>K<sub>i</sub> = 2.50 μM). On the other hand, 3,4-dimethoxy substitution of phenyl ring B afforded the best A<sub>2A</sub> adenosine receptor binding (A<sub>2A</sub>K<sub>i</sub> = 2.81 μM) among the quinazolinones investigated. In conclusion, the quinazolinones are ideal lead compounds for further structural optimization to gain improved adenosine receptor affinity, which may find therapeutic relevance in Parkinson's disease-associated cognitive deficits and motor dysfunctions as well as exerting neuroprotective properties.