Inherently, Graphene - a perfect 20 hexagonal crystal of C-atoms, is a non-spintronicsrnmaterial due to spin moment cancellation of C-atoms, especiall y, at the edges.rnSpintro nics, or spin electronics, involves the study of acti ve control and manipul at ion ofrnspin degrees of freedom in the solid-state systems with non- equili brium spin populations.rnThe spins transport can be introduced either by doping or creating exotic nanostructuresrnof graphene such as antidots. We have performed a systematic simulational study of barernand doped graphene nanostructures for their spin transport properti es. We studi ed therntransport properties of eight different O-shaped graphene nanoantidots (GNAOs) withrndi ffe rent electrode contact configurations by using non-equili brium Green' s functionsrn(NEGF) in combination with the density-functional theory (OFT). Our calculationsrnindicate the presence of spi ntro ni city in the graphene nanoanti dot 's GNAOs' geometricalrnconformations. Among the two important antidots (0 [, and O2,) , it is found that thernformer is more spintronic in comparison to the latter structure. Surprisingly, Oh becomesrnmore spintronic when the device is connected asymmetrically to its electrodes. This spinrnflip behavior is suitably ex plained in the thesis on the basis of zigzag edge spin-chargerncontributions to the devices. We have also studied effect of the presence of Co atom atrncenter of GNAO on its spintronicity -- by comparing spin up and spin down conductionrnchannel s. The prospects of spin control among graphene nanostructures for spintronicsrnapplications are also discussed in the thesis.