This open label, 2-part study will evaluate the safety and efficacy of RO5083945 in combination with standard chemotherapy in patients with advanced or recurrent non-small cell lung cancer who have not received prior chemotherapy. In Part 1 patients will receive RO5083945 intravenously and standard chemotherapy (cisplatin plus either gemcitabine or pemetrexed) for up to 6 cycles of 3 weeks and then RO5083945 until disease progression. In Part 2 patients will be randomized to receive either RO5083945 in combination with standard chemotherapy or chemotherapy alone for up to 6 cycles. In the absence of disease progression, patients receiving RO503945 can continue treatment with RO5083945 as monotherapy.

Inclusion Criteria:

• Adult patients, >/=18 years of age
• Advanced (IIIb), metastatic (IV) or recurrent non-small cell lung cancer
• At least 1 measurable disease lesion as per RECIST criteria
• Confirmed presence of EGFR in tumor tissue
• ECOG performance status 0-1
• Adequate hematological, renal and liver function

Exclusion Criteria:

• Prior chemotherapy or treatment with another systemic anti-cancer agent
• Radiotherapy within the last 4 weeks, except for limited field palliative radiotherapy for bone pain relief
• Symptomatic or active CNS metastases
• Recent history of poorly controlled hypertension (systolic >180mmHg or diastolic >100mmHg)
• Requirement for steroids > 40 mg prednisolone