rmidazo[1,2-α]pyridine derivatives of Formula (Ia) and pharmaceutical compositions thereof that modulate the activity of the 5-HT2A serotonin receptor. Compounds and pharmaceutical compositions thereof are directed to methods useful in the treatment of insomnia, dyssomnia, parasomnia and related sleep disorders, platelet aggregation, coronary artery disease, myocardial infarction, transient ischemic attack, angina, stroke, atrial fibrillation, thrombosis, asthma or symptoms thereof, agitation or symptoms thereof, behavioral disorders, drug induced psychosis, excitative psychosis, Gilles de Ia Tourette's syndrome, manic disorder, organic or NOS psychosis, psychotic disorders, psychosis, acute schizophrenia, chronic schizophrenia, NOS schizophrenia and related disorders, diabetic-related disorders, progressive multifocal leukoencephalopathy and the like. The present invention also relates to methods for the treatment of 5-HT2A serotonin receptor mediated disorders in combination with other pharmaceutical agents administered separately or together.