Pompe disease is a type-II glycogen storage disease, and clinical manifestations include hypertrophic cardiomyopathy and generalised muscular hypotonia. Enzyme replacement therapy has proven to be effective in reversing the ventricular hypertrophy. The outcomes are variable depending on time to diagnosis and severity of the cardiac disease. We describe two contrasting cases of patients with infantile-onset Pompe disease. The first child was diagnosed late and had severe cardiac hypertrophy with respiratory decompensation and ventilator dependence and eventual death. The second case was diagnosed at birth with early initiation of therapy resulting in a good outcome. Our cases highlight the importance of early initiation of enzyme replacement therapy to improve clinical outcomes.